High Performance Breath Alcohol Analysis1147109/FULLTEXT05.… · High Performance Breath Alcohol...

Mälardalen University Doctoral Dissertation 240

High Performance Breath Alcohol AnalysisJonas Ljungblad

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ISBN 978-91-7485-350-6ISSN 1651-4238

Address: P.O. Box 883, SE-721 23 Västerås. SwedenAddress: P.O. Box 325, SE-631 05 Eskilstuna. SwedenE-mail: [email protected] Web: www.mdh.se

Mälardalen University Press DissertationsNo. 240

High PerformanceBreath Alcohol Analysis

Jonas Ljungblad

2017

School of Innovation, Design and EngineeringMälardalen University

Copyright c© Jonas Ljungblad, 2017ISSN 1651-4238ISBN 978-91-7485-350-6Printed by E-Print AB, Stockholm, Sweden

Mälardalen University Press DissertationsNo. 240

HIGH PERFORMANCE BREATH ALCOHOL ANALYSIS

Jonas Ljungblad

Akademisk avhandling

som för avläggande av teknologie doktorsexamen i elektronik vid Akademinför innovation, design och teknik kommer att offentligen försvaras onsdagen

den 15 november 2017, 09.15 i Delta, Mälardalens högskola, Västerås.

Fakultetsopponent: Professor Olof Lindahl, Umeå university

Akademin för innovation, design och teknik

AbstractAlcohol breath testing on a larger scale will save lives. Alcohol intake affects the human body by significantly longer response time to external stimuli. In demanding situations where the senses need to be on alert a prolonged reaction time can be the difference between life and death, both for the intoxicated subject and for surrounding individuals.

The aims of this thesis include investigations of a new type of breath alcohol sensor, designed for operation without a mouthpiece, both with regards to sensor performance as well as usability in relation to various breath alcohol screening applications.

In many situations where breath alcohol screening is suitable, there is a need for quick and easy use. The instrument should interfere as little as possible with the regular routines and procedures. One such task is driving. To accommodate for these needs in an in-vehicle application, the breath alcohol sensing system must be seamlessly installed in the vehicle and not interfere with the normal behavior of the sober driver. Driving is also a task requiring high level of concentration over a prolonged period of time. In the U.S. alone thousands of lives are annually lost in accidents where the driver was under the influence of alcohol. Similar numbers have been recorded for Europe. The potential for a system handling the needs for ease-of-use is huge and may result in successful products.

The results presented within this thesis provide experimental evidence of sufficient sensor performance for screening applications with an instrument operating without a mouthpiece. Smarter calculation methods were also shown to be a feasible path to improved measurement reliability. Important steps towards an even more passive solution for in-vehicle screening is also presented. Experiments showed that given enough time and sensor resolution, passive alcohol detection systems are feasible.

ISBN 978-91-7485-350-6ISSN 1651-4238

Abstract

Alcohol breath testing on a larger scale will save lives. Alcohol intakeaffects the human body by significantly longer response time to externalstimuli. In demanding situations where the senses need to be on alerta prolonged reaction time can be the difference between life and death,both for the intoxicated subject and for surrounding individuals.

The aims of this thesis include investigations of a new type of breathalcohol sensor, designed for operation without a mouthpiece, both withregards to sensor performance as well as usability in relation to variousbreath alcohol screening applications.

In many situations where breath alcohol screening is suitable, thereis a need for quick and easy use. The instrument should interfere as littleas possible with the regular routines and procedures. One such task isdriving. To accommodate for these needs in an in-vehicle application, thebreath alcohol sensing system must be seamlessly installed in the vehicleand not interfere with the normal behaviour of the sober driver. Drivingis also a task requiring high level of concentration over a prolonged periodof time. In the U.S. alone thousands of lives are annually lost in accidentswhere the driver was under the influence of alcohol. Similar numbershave been recorded for Europe. The potential for a system handling theneeds for ease-of-use is huge and may result in successful products.

The results presented within this thesis provide experimental evi-dence of sufficient sensor performance for screening applications with aninstrument operating without a mouthpiece. Smarter calculation meth-ods were also shown to be a feasible path to improved measurementreliability. Important steps towards an even more passive solution forin-vehicle screening are also presented. Experiments showed that givenenough time and sensor resolution, passive alcohol detection systems arefeasible.

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Sammanfattning

Alkohol p̊averkar människokroppen negativt genom bland annat ned-satt reaktionsförmåga. I koncentrationskrävande situationer kan reak-tionsförmågan ha en väldigt viktig roll och kan vara avgörande för attundvika katastrofala olyckor med dödsfall som p̊aföljd. Exempelvis för-loras tusentals liv årligen runt om i världen p̊a grund av rattonykterhet.

Arbetet som presenteras i den här avhandlingen innefattar under-sökningar av en ny sensor avsedd för mätning av utandningsalkoholutan att använda ett munstycke. Dels har sensorprestanda undersöktsi relation till relevanta industriella tillämpningar och dels har undersök-ningarna fokuserat p̊a att förenkla provtagning för användaren.

I många applikationer där det finns ett behov av alkoholtestning, ärenkelhet och tiden det tar att genomföra testet av stor betydelse. Instru-mentet bör störa de vanliga rutinerna i s̊a liten utsträckning som möjligt.Vid användning i bil stämmer detta väldigt väl. Ingen vill sitta och väntap̊a att ett instrument ska initieras innan det är möjligt att köra iväg.Enkelhet är ledordet för instrument där daglig användning tillämpas.För bilmiljön betyder detta diskreta installationer där mätprocesseninte p̊averkar den nyktra föraren. Potentialen för ett system som kanhantera behovet av enkelhet vid provtagning är enorm och kan resulterai framg̊angsrika produkter.

Avhandlingen inneh̊aller resultat som visar att prestandan för dennya sensorn är tillräcklig för mätning av utandningsalkohol d̊a instru-mentet används utan munstycke. Avhandlingen inneh̊aller ocks̊a viktigasteg mot en mer passiv lösning där syftet är att avgöra om bilföraren ärp̊averkad av alkohol eller ej.

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Acknowledgements

Throughout my studies and work I have met many interesting and knowl-edgeable people. They have provided guidance, insight and support. Iwould therefore like to express my most grateful appreciation for all yourefforts.

First of all, founder of Hök Instrument AB and research guru as wellas my co-supervisor, thank you Dr. Bertil Hök. Thank you for yourendless interest in everything new and your out of the box thinking. Youhave been an inspiration and provided vital guidance in the world of re-search.

My supervisor, Dr. Mikael Ekström, thank you for your support-ive and positive attitude. Our discussions were highly appreciated andyour participation was most welcome.

Thank you to all the people at Hök Instrument AB, for taking thecompany forward and making it an interesting place to work and do re-search.

The leadership from H̊akan Petterson and Alf Holgers and the workperformed by Autoliv Development AB was of utter importance foracquiring the successful results shown in this thesis and their efforts cannot be acknowledged enough. Thank you.

To all the people involved at Senseair AB, including Dr. Hans Mar-tin, Dr. Henrik Rödjeg̊ard, Erik Wilhelmsson, Dr. ChristineHummelg̊ard and many more, thank you for the fruitful collaborationin the alcohol sensor development projects!

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I would also like take the opportunity to express my gratitude towardsall people involved in the DADSS program. Dr. Abdullatif Zaouk,Michael Willis and the rest of you at KEA Technologies for your be-lief in presented solutions and for providing a constructive environment,thank you. Thank you Rob Strassburger and ACTS, your vision andeffort is of utter importance for the continuation of the program.

Thank you Dr. Lars Tenerz and you Raimo Gester for provid-ing me with the opportunity to combine work and research.

Thank you Dr. Annika Kaisdotter Andersson, for ”paving theroad” with your research. Your support in the human subject studieswas greatly acknowledged.

Thank you Dr. Mats Enlund for your input and support duringthe human subject studies. And thank you Sofia Tenerz and Marja-Leena Ojutkangas for your help during said studies.

Mathias Granstam you deserve a special mention. You are alwaysopen for discussions, no matter the topic. Your presence have broughtmany laughters to House 24.

The Its-Easy research school andESS-H research profile atMälar-dalen University has also contributed to my progress over these lastyears. Thank you.

The perhaps most important, however unprofessional, thank you goesto my friends and family, who understand the importance of havingfun! Te och gifflar kan inte underskattas!

Jonas LjungbladVäster̊as, September, 2017

List of publications

Paper ACritical Performance of a New Breath Alcohol Analyzerfor Screening Applications, Jonas Ljungblad, Bertil Hök, MikaelEkström, 2014 IEEE Ninth International Conference on IntelligentSensors, Sensor Networks and Information Processing (ISSNIP),Singapore, April, 2014.

Paper BUnobtrusive and Highly Accurate Breath Alcohol Anal-ysis Enabled by Improved Methodology and Technology,Bertil Hök, Jonas Ljungblad, Annika Kaisdotter Andersson, MikaelEkström and Mats Enlund, Journal of Forensic Investigation, 2014.

Paper CUnobtrusive Breath Alcohol Sensing System, Bertil Hök,H̊akan Pettersson and Jonas Ljungblad, The 24th InternationalTechnical Conference on the Enhanced Safety of Vehicles, Gothen-burg, Sweden, June 8-11, 2015.

Paper DDevelopment and Evaluation of Algorithms for Breath Al-cohol Screening, Jonas Ljungblad, Bertil Hök and Mikael Ek-ström, Sensors, 2016.

Paper EExperimental Proof-of-Principle of In-Vehicle Passive BreathAlcohol Estimation, Jonas Ljungblad, Bertil Hök and H̊akanPettersson, The International Council on Alcohol, Drugs and Traf-fic Safety, Gramado, Brazil, October 16-19, 2016.

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Paper FPassive In-Vehicle Driver Breath Alcohol Detection Us-ing Advanced Sensor Signal Acquisition and Fusion, JonasLjungblad, Bertil Hök, Amin Allalou and H̊akan Pettersson, Traf-fic Injury Prevention, 2017.

Author’s contribution

Paper AMy contribution to the paper include all experiments, measure-ments, analysis and data interpretation. I also took part in writingthe manuscript.

Paper BI designed and implemented the measurement algorithm in a Lab-View real-time interface. I designed the human subject study set-up, participated largely in the measurements, performed the dataanalysis and evaluation and took part in writing the manuscript.

Paper CI designed and performed in-vehicle experiments and evaluated thedata.

Paper DIn this paper I contributed with the idea. I developed the algorithmand performed data analysis. I also contributed in writing themanuscript.

Paper EI contributed to the idea, performed the experiments and dataevaluation. I also wrote a large part of the paper.

Paper FI participated largely to the planning of the paper, execution ofexperiments as well as analysis.

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Abbreviations

AC Alcohol ConcentrationAlcohol In this context synonymous with

Ethyl AlcoholBAC Blood Alcohol ConcentrationBrAC Breath Alcohol ConcentrationCO2 Carbon DioxideCNS Central Nervous SystemDF Dilution FactorDUI Driving Under the InfluenceEtOH Ethyl AlcoholFEM Finite Element MethodH2O WaterIR InfraredM-M Michaelis-MentenN2 NitrogenNDIR Non-Dispersive InfraredNIR Near-InfraredO2 OxygenRMS Root Mean SquareUV Ultra Violet

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Contents

1 Introduction 19

2 Background 232.1 History of breath alcohol determination . . . . . . . . . . 232.2 Alcohol in the body . . . . . . . . . . . . . . . . . . . . . 24

2.2.1 Alcohol impairment . . . . . . . . . . . . . . . . . 242.2.2 Absorption of ethanol . . . . . . . . . . . . . . . . 242.2.3 Elimination of ethanol . . . . . . . . . . . . . . . . 252.2.4 Relation to exhaled alcohol concentration . . . . . 26

2.3 Measuring alcohol intoxication . . . . . . . . . . . . . . . 272.3.1 Breath alcohol sensors . . . . . . . . . . . . . . . . 28

2.4 Recent advancements . . . . . . . . . . . . . . . . . . . . . 302.5 Sampling without a mouthpiece . . . . . . . . . . . . . . . 32

3 Research methods 353.1 Measurement principle and sensor implementation . . . . 353.2 Investigations of sensor performance . . . . . . . . . . . . 363.3 Human subject studies . . . . . . . . . . . . . . . . . . . . 39

3.3.1 Note on ethics in relation to the human subjectstudies . . . . . . . . . . . . . . . . . . . . . . . . . 41

3.4 In-vehicle investigations . . . . . . . . . . . . . . . . . . . 41

4 Results 454.1 Investigations of sensor performance . . . . . . . . . . . . 454.2 Human subjects studies . . . . . . . . . . . . . . . . . . . 474.3 In-vehicle investigations . . . . . . . . . . . . . . . . . . . 49

5 Discussion 53

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xvi Contents

6 Conclusions 57

7 Future work 59

Bibliography 61

List of figures

2.1 Ethanol time profile for both venous blood and breathalcohol. Data collected during human subjects test. . . . . 26

2.2 IR-spectrum of ethanol and carbon dioxide. Spectrumdata was collected from [1]. . . . . . . . . . . . . . . . . . 30

3.1 Chamber used for calibration of prototypes. . . . . . . . . 37

3.2 Humid gas generator used to simulate a human exhalation. 38

3.3 Human subject performing a breath test into a hand helddevice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.4 Vehicle used for in-vehicle experiments shown at an exhi-bition in conjunction with the ESV conference in Gothen-burg, 8-11 June 2015. . . . . . . . . . . . . . . . . . . . . 42

3.5 Breath alcohol sensor integrated into the steering columncover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3.6 a) Experimental setup for in-vehicle testing of gas pulses.b) Simulation of in-vehicle breath distribution. . . . . . . 43

4.1 The resolution of the sensor at different time frames wasdeduced by the use of Allan deviation. At 1 second in-tegration time, approximately the time of a human ex-halation, the resolution of the sensor was determined to0.0009 mg/L. . . . . . . . . . . . . . . . . . . . . . . . . . 46

4.2 a) Measured dilution factor at increasing distance. b)Measured alcohol at increasing distance. . . . . . . . . . . 47

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xviii List of figures

4.3 Results from a human subjects study. Both panels showthe data evaluated as a classifier with an allowed toleranceinterval set for a specified cut off value. The upper panelshows the results in relation to the Swedish limit at 0.1mg/L and the relation is made to the European limit at0.25 mg/L in the lower panel. . . . . . . . . . . . . . . . . 48

4.4 Left: Sensor output without any modifications made tothe measurement algorithm. Right: Sensor output withthe two methodological improvements implemented. . . . 49

4.5 Dilution measured at various sensor positions inside thevehicle compartment. The blue, red and black lines showthe concentration of alcohol in a diluted breath samplebased on the intoxication level. . . . . . . . . . . . . . . . 50

4.6 Signals measured from an intoxicated subject. Uppergraph: CO2 concentration increase. Lower graph: Ethanolconcentration increase. . . . . . . . . . . . . . . . . . . . . 51

4.7 a) Simulated breath-by-breath recording of alcohol (lower)and CO2 (upper) concentrations. b) Experimental record-ing of in-vehicle sensor signals using gas pulses from thesetup depicted in figure 3.6, CO2 (top graph) and alcohol(bottom graph). . . . . . . . . . . . . . . . . . . . . . . . . 52

Chapter 1

Introduction

Alcohol impaired driving increases the risk of traffic accidents dramat-ically. In fact, the risk of being in an accident increases exponentiallywith the degree of intoxication [2]. 145 drivers lost their lives on Swedishroads in 2012. Out of these 18% proved to be alcohol related [3]. Thenumber increased slightly in 2016 to 152 fatalities with 22% of theseproven to be under the influence of alcohol [4]. In the U.S. the numberof accidents with fatal outcome involving alcohol impaired drivers was10265 in 2015; this represented 29% of all traffic related deaths [5].

The current state of the art breath alcohol analysers demand deliveryof a forced expiration with a mouthpiece. In everyday use where timeand effort need to be minimized, e.g. vehicle and high trough-put appli-cations, the mouthpiece is a limiting factor. Therefore there is a needfor technological advancements to address the challenges for ease-of-usewhile maintaining the reliability of the measurement.

As a result of an industrial partnership between Autoliv, Imego andHök Instument AB, a method for effortless breath alcohol determinationwas proposed by Hök et al. in 2006 [6]. The method is based on thefact that CO2 is produced in the human body via cellular respirationand in an exhalation the variation in CO2 concentration is sufficientlylow between individuals and breaths. CO2 can therefore be used as atracer gas to account for the dilution of a breath sample. The viabil-ity of CO2 as a tracer gas was studied by Kaisdotter Andersson, whichresulted in a PhD thesis in 2010 [7]. The method showed promisingresults allowing for continued development of user friendly breath alco-

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20 Chapter 1. Introduction

hol interlocks. Senseair AB was involved at an early stage contributinggreatly with a strong background in gas sensor technology and highvolume IR-sensor manufacturing. For several years the research anddevelopment effort was conducted as a collaboration between Autoliv,Hök Instrument and Senseair. The progress made in the project at-tracted international attention and support has been received from anAmerican public and private partnership. The National Highway Traf-fic Safety Administration (NHTSA) and the Automotive Coalition forTraffic Safety (ACTS) together have undertaken the task to encouragenew technology research to eliminate drunk driving on American roads.The partnership is called the Driver Alcohol Detection System for Safety(DADSS) program. Within the program there is a strong belief that ifa system is to be accepted by the general public, even by people whodo not drink and drive, the determination of breath alcohol needs to beperformed without any extensive action by the user. The system alsoneeds to be accurate, fast, reliable, durable and maintenance free [8].The system should not inconvenience the sober driver. The program hasbeen a driving force to reach the extreme resolution required by such asystem and the highly set goals for unobtrusive alcohol determination.

The aim of this thesis is to further investigate the technology withthe focus to push the boundaries in terms of ease-of-use in relation tobreath alcohol sensing. My presented work includes investigation of sen-sor performance, human subjects studies and in-vehicle investigations.The lion share of the work has been focused on breath alcohol analysisin an vehicle environment. However, there are many important areaswhere the technology can be applied. Safety critical tasks are performedevery day at airports, building sites, power plants, etc. Mass screen-ing in such environments has the potential to minimise risk and savelives. The data collected during rigorous tests has been analysed in re-lation to various potential products in mind. The starting point was ahand-held device capable of measuring exhalations at a distance of a fewcentimetres. Throughout the studies the investigated distance betweenthe mouth and device increased, and with that an increased dilution.As the dilution increases so does the demand for higher resolution. In avehicle environment, the ultimate goal is to achieve a system capable ofdetecting breath alcohol from an intoxicated driver without active hu-man interaction. Translated to the application, it means capability tomeasure tidal breathing at a distance of approximately 65 cm.

The investigated method and technology is one of two remaining

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technologies selected for the DADSS initiative. The other technology isbased on transdermal infrared spectroscopy [9, 10]. Our technology hasbeen validated for breath alcohol determination at short distances withlow dilution, however there is still a gap to a truly passive system. Thework presented herein shows steps toward the visionary technology.

Chapter 2

Background

2.1 History of breath alcohol determination

Scientific research on breath alcohol in relation to overconsumption ofalcohol dates back to 1874 when Anstie published his Final experimentson the elimination of alcohol from the body. Anstie showed that only afraction of the consumed alcohol could be recovered in the breath.

In the 1930s blood alcohol concentration studies were performed byErik Widmark in Sweden when he established concentration-time pro-files of ethanol [11]. Liljestrand and Linde shortly thereafter found highcorrelation between blood and breath ethanol concentration and deter-mined a constant blood:breath ratio of 2000:1. They also reported atime dependency of the blood-to-breath ratio depending on the time af-ter drinking [12]. At first, legal limits were only set for blood alcoholconcentrations causing a prolonged debate regarding an accurate con-version factor. However, due to the time dependence between bloodand breath alcohol, most countries nowadays utilize one limit for bloodalcohol and one for breath alcohol [11].

The first breath alcohol measurement device for use by law enforce-ment was invented and designed by Robert Borkenstein at Indiana Uni-versity in 1954 [11]. He utilized an oxidation/reduction wet chemistryreaction between alcohol and potassium dichromate to measure the ab-sorption difference with UV spectroscopy [13].

The first alcohol interlocks were introduced in the late 20th centuryfor conditional withdrawal of driver’s license for people sentenced for

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24 Chapter 2. Background

drunk driving - with varying success. Sweden was in fact able to presentone of the few success stories, due to the important rehabilitation activ-ities that were linked to the actual use of acohol interlocks. The mostimportant contribution to the development of alcohol interlocks was inuse for quality assurance of transport services. Pioneering work wasperformed by the Swedish Road Administration in collaboration with anumber of visionary companies in the transport sector. Within a fewyears, a de facto standard was established [7].

2.2 Alcohol in the body

2.2.1 Alcohol impairment

Alcohol affects almost all organs in the human body. The most pro-nounced effects when performing a complex task, e.g. driving, are re-lated to the central nervous system. Alcohol impairs several importantphysiological functions, including vision and reaction time [11]. Alco-hol also interferes with the ability to see objects at greater distance,diminish peripheral vision and impairs feature extraction in low lightconditions. Apart from identifying a potential risk, the brain also has todecide how to avoid an imminent accident and a response signal has tobe sent through the nerves to the muscles [11]. Alcohol delays each stepin the signaling sequence and as a result the response time will increase.The risk increase due to alcohol impaired driving has been studied onseveral occasions, [14, 2]. The studies are unanimous in that the risk ofbeing in a car accident is increasing with the amount of alcohol in thebody. The risk increase follows an exponential pattern versus the levelof intoxication. The effects of alcohol start at very low concentrations,but a profound risk increase will not occur until reaching higher alcoholconcentrations in the body [2].

2.2.2 Absorption of ethanol

The usual way to introduce alcohol to the body is through the mouth.As the alcohol reaches the stomach the absorption slowly starts throughthe stomach wall. The largest part of the ingested alcohol will how-ever be absorbed after gastric emptying, in the duodenum and the smallintestine [11]. The absorption of alcohol to the body follows a pharma-cokinetic profile with large variation. The variation is caused by many

2.2 Alcohol in the body 25

factors, including age, gender, liver status, stomach content, concentra-tion of the devoured liquid, etc [11]. The absorbed alcohol travels fromthe intestinal tract with venous blood through the hepatic vein and dis-tributes throughout the entire body. Due to the solubility of alcohol inwater, the small size of the molecule itself and the sheer amount of wa-ter in the human body, approximately 50-60% of the total body weight,alcohol makes its way into almost all compartments of the body [11].

2.2.3 Elimination of ethanol

Most ethanol, approximately 95%, in the body is removed through oneout of three possible enzyme catalysed processes. In all three processes,ethanol is metabolised into acetate via the intermediate acetaldehyde.The main pathway of the metabolism accounts for approx. 94% ofthe ingested ethanol uses the enzyme alcohol dehydogenase, an enzymeabundant in liver cells, to metabolize ethanol to acetaldehyde. By theassistance of aldehyde dehydrogenase acetaldehyde is i turn metabolisedinto acetate, which enters the normal metabolism with CO2 and H2O asthe end products.

Less than 0.1% of the dosed ethanol metabolises anaerobic to formethyl glucuronid and ethyl sulfate. These substances can be found inurine after drinking.

The rest of the ethanol, approximately 5%, is excreted form the bodyunchanged in breath, sweat and urine.

Typical ethanol-time profiles are given in figure 2.1. Ethanol, whenconsumed, is consumed in large quantities compaired to other impairingsubstances. The main pathway for the body to eliminate the substanceis through enzyme catalysed reactions. This leads to saturation of theinvolved enzymes. The reaction therefore follows a linear curve until theconcentration of ethanol is low enough to no longer occupy every avail-able enzymatic space. At this point the elimination no longer appearlinear, but instead shows a non-linear time curve. The transition occursat ethanol concentrations as low as 0.01-0.02 g/L in blood. Eventhoughthe elimination more closely follows M-M kinetics [15], most forensic cal-culations of blood ethanol utilize the linear appearance of the saturatedelimination reaction.


Figure 2.1: Ethanol time profile for both venous blood and breath alco-hol. Data collected during human subjects test.

2.2.4 Relation to exhaled alcohol concentration

The exchange of ethanol to inspired air occurs throughout the entireairways. Alveoli are surrounded by capillaries. The ethanol carried inthe blood will diffuse across the alveolar/capillary membrane and anequilibrate state between the liquid and the gas will be established. Inthe alveoli, the gas holds a constant temperature of 37◦C [16]. During theexpiration, the alveolar air comes in contact with the mucous membraneof the upper airways. These are also saturated with ethanol. In theupper airways, the temperature of the gas is lowered to 34◦C and thegas will not hold as high concentration of ethanol as in the alveoli. Inthis part of the airway the gas is re-equilibrated to the new ambientconditions [16, 17].

There are many sources of variation affecting the final exhaled breathalcohol concentration. An increased body temperature will increase themeasured BrAC [18] and likewise will a decrease in core body temper-ature decrease the BrAC [19]. The conditions of the inhaled air with

2.3 Measuring alcohol intoxication 27

regards to temperature and humidity will influence the BrAC [20]. Dif-ferences in breathing pattern will also provide variations in the resultingBrAC. Hyperventilating may decrease the BrAC by as much as 20%while breath holding may increase the BrAC by up to 15% [16].

Comparing blood and breath alcohol shows good correlation, butare two different practices that vary over time during the intoxicationperiod. Thus, converting from breath alcohol to blood alcohol is notconsidered best practice. Breath alcohol testing methods is howeverconsidered viable for both screening and evidential purposes and todaymost countries have statutory limits for both methods [11, 21].

2.3 Measuring alcohol intoxication

Alcohol is present in intoxicated persons throughout the entire humanbody. Analysis of blood or breath samples are the two most commonlyused species. Possibilities are however present to analyse the ethanolconcentration in several human samples, such as urine, saliva or evendirectly in tissue [11], each methodology has its own pros and cons.

Blood alcohol analysis for instance is expected to closely reflect thealcohol concentration experienced by the brain. Since the brain is themost important organ effected during alcohol intoxication, especially incomplex situations, this is a favourable property. Most blood analysis ishowever performed on venous blood, which is not as good of an estimatorof CNS impairment as arterial blood, especially in the absorptive phase[22]. The techniques for sample preparation are also intrusive by natureand require a penetration of the subjects’ skin. The risks associated witharterial puncture is relatively high and therefore venous blood is moreregularly used [11].

Breath alcohol analysis is favourable in the non-intrusive nature ofthe sample preparation. The techniques also allow for on-site testingwith a readout within seconds. The analysed breath is however never indirect contact with the brain, but instead with various parts of the res-piratory system. Blood is the carrier of alcohol to all parts of the bodyincluding these tracts. As previously mentioned studies have shown goodcorrelation between blood and breath alcohol with physiological varia-tions present [11, 21, 23]. The correlation is also better when comparingbreath to arterial blood alcohol than to venous blood alcohol and is agood indicator for CNS impairment[24].


Urine alcohol analysis has also proven itself a viable method for al-cohol intoxication testing. Analysis of urine samples are not as intrusiveas blood analysis. On the down side, correlation to blood alcohol levelsshow huge variation [25]. The variation also shows a dependency on timeafter drinking [23]. Usual testing therefore requires a two test method-ology, i.e. a second test is carried out 20 to 30 minutes after the firstone [11].

Saliva is another possibility of analysis [23]. Testing can be donerelatively non-intrusively. Single use screening tests are available basedon a colorimetric method, with test results available within minutes.For high accuracy measurements laboratory methods and equipment isrequired.

An emerging technology makes use of the distribution of alcoholthroughout body and non-invasive measurement in the subjects tissue[9, 10]. The technology makes use of NIR spectroscopy. Light penetratesthe skin to a depth of several millimeters and ensures measurement inthe dermal layer of the skin. Reflected light is collected and analysedusing an interferometer [10].

2.3.1 Breath alcohol sensors

There are several technologies available to capably and readily determinethe level of intoxication in the human body [26, 27, 28]. Most systemsare based on one out of three technologies, i.e. fuel cell sensors, semicon-ductor sensors or infrared spectrometry. The majority of the availablesystems are using a mouthpiece to direct the breath undiluted to thesensor core.

Today the most widely used technology is electrochemical fuel cells.Fuel cell sensors originates from the development of fuel cells as a meansto produce electrical power. The fuel cell sensors operate by using theexhaled ethanol in a humans breath as a fuel. The cell is comprised ofan anode and an electrode separated by an electrolyte semi permeablemembrane. The cell also includes a wire between the two electrodes.At the anode ethanol is oxidized to acetic acid, free electrons and hy-drogen ions. At the cathode oxygen make use of the free electrons andhydrogen ions to form water. The current produced by the reactionis proportional to ethanol concentration of the sample and is used foranalytical purposes [29]. Fuel cell based sensors are considered to beaccurate and precise. Fuel cells rely on catalytic surfaces [30], prone

2.3 Measuring alcohol intoxication 29

to sensitivity variation upon use. Frequent recalibration is therefore re-quired. Instruments based on fuel cell technology are used in a varietyof different applications including alcohol interlocks, screening devicesas well as evidential equipment.

Semiconductor elements is another type of sensors used for breathalcohol measurements. The main advantage of this type of sensors isthe low cost and high sensitivity [31]. In a semiconductor sensor ethanoladsorbs to the sensor surface. The conductivity of the sensor elementis thereby changed in proportion to the concentration of the gas. Theconductivity change can be converted into a readable output voltage [29].Semiconductor based breath alcohol instruments primarily focus on low-cost consumer markets. Many instruments suffer from low selectivityand low accuracy and precision.

Another technique widely employed by law enforcement utilizes NDIRmeasurement cells. The technique is recognized for high accuracy andprecision as well as high specificity. A typical set-up includes an emit-ter, a detector and a measurement cell. In IR-spectroscopy each specificmolecule rotates and vibrates in a unique pattern and therefore absorbsIR-light of different wavelengths with varied intensity. In the instrument,the light emitted from a black body radiator passes through an opticalcell with a fix optical path. As the specific substances, e.g. ethanol, fillthe cell the transmitted light is reduced and therefore indicates molecularabsorption. The ratio between the transmitted light intensity, I, and thetransmitted light at zero gas concentration, I0, is called transmittance,T, and is calculated according to:

T =I

I0(2.1)

For the analysed wavelength each substance has a specific molar absorp-tion coefficient, ε, which defines the capacity of the substance to absorblight. The intensity of the transmitted light is also dependent on thelength the light travel through the media and the concentration of theanalysed substance. Together this gives the Beer-Lambert’s law:

I = I010−ε[J]l (2.2)

Beers-Lambert’s law can be rewritten as an absorbance function accord-ingly:

A = logI0I

= ε[J ]l (2.3)


Beers-Lambert’s law states that low concentrations need long op-tical path in order to receive high absorbance [30]. Figure 2.2 showsabsorbance curves from ethanol and carbon dioxide respectively. Wave-lengths analysed in our system are visible within the dotted lines.

Figure 2.2: IR-spectrum of ethanol and carbon dioxide. Spectrum datawas collected from [1].

The main application for instruments based on IR-spectroscopy isfor evidential purposes. The technology has inherently good qualitiesincluding high accuracy, precision, specificity, reliability and calibrationstability. Compared to the other sensor alternatives the cost is towardsthe high end of the spectrum. Since the sensitivity of the system isproportional to the optical path of the measurement cell there are issuesrelated to miniaturisation.

2.4 Recent advancements

One major problem with the alcometers was the prolonged exhalationsneeded for an approved breath test. This issue was addressed by Hök etal. in 2006 by simultaneous measurement of ethanol and carbon dioxide

2.4 Recent advancements 31

in the same cavity [6]. The device did not include a mouthpiece; insteadthe measured carbon dioxide was related to the proposed alveolar carbondioxide concentration in order to measure the dilution of the breathsample [6]. In 2010 Annika Kaisdotter Andersson defended her PhDthesis Improved Breath Alcohol Analysis with Use of Carbon Dioxide asthe Tracer Gas at Mälardalens Högskola which further strengthened thefindings of Hök et al. and showed sufficient performance for alcolocksand screening devices [7]. The ease of use enabled alcohol measurementsin situations previously deemed unsuitable for alcometers, e.g. subjectswith depressed consciousness [32, 33].

So far, the research has focused on directed breaths at short distancebetween the mouth and the alcohol measurement device. However, re-cently the first steps towards breath alcohol determination in highlydiluted breath samples were taken by Kaisdotter Andersson et al. [34].These investigations were triggered by a request from our industrial part-ners (Autoliv, DADSS [35, 36, 8, 37]) who believe an alcohol meter whichrequires minimal attention will provide a wider acceptance for vehicle al-cohol interlocks. Passive detection of breath alcohol has previously beeninvestigated using a pre-amplification procedure to increase the concen-tration of the alcohol at the sensor location [38]. The method showedpromise, but also inherent difficulties with time to detection.

In the DADSS program alcohol impaired driving is targeted as a fo-cus research area aimed at reducing the number of deaths on Americanroads. Within the program, there is consensus between the governmen-tal agency NHTSA and several car manufacturers in that the technologycurrently available on the market is too intrusive in their execution formass deployment. Instead, the technology needs to be non-intrusive, reli-able, durable, maintenance free and should not interfere with the normalactivities of the driver [35, 8]. The motivation for stringent demands onthe technology is based on the belief in a non-regulatory path to combatthe issue at hand.

However, a truly passive alcohol detection system does increase thedemands on the system and several challenges need to be investigated.As the dilution increase, the concentrations decrease to extremely lowlevels. The sensor must therefore exhibit high resolution. An entirelypassive system is the vision, but there are several challenges that needinvestigation on the way, e.g. the influence of passengers in the vehiclecompartment. Scientific evidence with respect to feasibility of unobtru-sive breath alcohol determination as well as sufficient performance is of


the essence.Regardless of the dilution, an automotive system also needs to func-

tion properly in a wide variety of environments and conditions. Manyspecified cases can be found in the European standard for alcolocks[39, 40].

2.5 Sampling without a mouthpiece

In order to measure breath alcohol levels at a distance without a mouth-piece there is a need to measure the dilution of the sampled gas. Inhuman breath two IR-active gases are in abundance; carbon dioxide andwater. Due to the relatively low interindividual end-expiratory concen-tration variation between different humans, both gases have been consid-ered for use as a reference [41, 42]. Kaisdotter Andersson proclaimed thatthe risk of underestimating the breath alcohol concentration is reducedby the use of carbon dioxide as the reference gas [7] and accordinglyis used in our system today. The breath alcohol concentration (BrAC)is calculated by multiplying the level of dilution (quotient between theend expiratory and the measured carbon dioxide concentration) with themeasured alcohol concentration (AC):

BrAC =CO2alvCO2meas

AC (2.4)

CO2 is an endogenous gas produced in the mitochondria locatedin cells throughout the entire body. The blood carries CO2 to thepulmonary capillaries surrounding the alveoli. The CO2 passes capil-lary/alveolar membrane into alveolar gas [43]. The true value of of theconstant CO2alv in equation 2.4 has been the subject of various inves-tigations [44, 45] and has been reported to be influenced by breathingpattern [46] or exercise [47]. Naturally occurring variation between dif-ferent subjects has also been reported [45]. These variations will influ-ence the BrAC output. The quotient CO2alv/CO2meas is also affectedby the background CO2 concentration in ambient air. Current reportson outdoor CO2 sets an ambient concentration of 400 ppm [48]. In othermeasuring environment, e.g. indoor or vehicle interior, the value mayvary from 350 ppm up to 5000 ppm [49, 50]. At low to moderate dilu-tions, i.e. short distances, the influence from the background is very low.As the dilution increases, so will the influence from a reliable background

2.5 Sampling without a mouthpiece 33

measurement. Recently, products using the methodology has been de-ployed by a nationwide train company in Sweden, where all train driversare tested before every shift [51].

Albarda patented [52] the use of water as a tracer gas for determiningthe blood alcohol level in 1979. The method is similar to equation 2.4with water instead of CO2. The methodology was implemented in in-strumentation by Olsson [42, 53] and deployed in entry ports in Sweden[54].

Chapter 3

Research methods

The work included in the thesis regards a new generation of breath al-cohol sensor. The first part of the investigation includes bench testingto explore sensor performance. The second part includes studies withhuman subjects to evaluate and gain understanding of variation causedby physiological parameters when measuring at a short to moderate dis-tance from the subject. And the third part is aimed towards passivealcohol detection in a vehicle environment based on discretely placedsensors. Results have been acquired by experimental set-ups, sensorsignal evaluation, statistical techniques and descriptive simulations.

3.1 Measurement principle and sensor im-plementation

The measurement principle allows for mixing of the sample with ambientair. This is made possible by using an endogenously produces raspira-toy gas as a normalizing factor. The methodology of using CO2 as atracer gas to account for the dilution has previously been thoroughlyinvestigated [6, 41, 55, 7, 46] and is the measuring principle employedthroughout this work. The basic calculation normalizes the measuredCO2 concentration to the expected expired CO2 concentration and mul-tiplies with the measured EtOH concentration to estimate the expiredbreath alcohol concentration, BrAC. The equation follows:

35

36 Chapter 3. Research methods

BrAC =CO2expCO2meas

AC (3.1)

The sensor is based on a NDIR design [56] employing a White cell[57] implementation. The sensor has two optical channels, one for CO2and one for EtOH. CO2 is measured at 4.26μm and the strong EtOHpeak at 9.5μm is used to quantify EtOH. The low alcohol concentrationin breath sets a requirement for a long optical path. This does not agreewith the requirement from the industry of a compact size. The sensoris therefore designed as a White cell [57], where two mirrors allow theemitted light to reflect several times in the same measurement cavityadding up to an appropriate optical path.

3.2 Investigations of sensor performance

The performance of the sensor prototypes has been thoroughly inves-tigated in a laboratory setting. There are small sensitivity variationsbetween sensor individuals, resulting from the manufacturing process.Therefore, all sensors have been subjected to a calibration procedure.The sensors were placed inside a closed compartment, Figure 3.1, anda precise amount of high grade ethanol was thereafter applied to thecompartment and allowed to evaporate. The procedure was repeated forseven concentrations and individual calibration parameters were calcu-lated and stored on a built-in memory. The technique was also used toinvestigate the sensitivity variation between sensors.

Apart from sensitivity, stability and noise set the detection limit forthe sensor system. Two different methods were applied in the evaluationof these two properties. Both include logging the sensor signal over time.The difference between the methods lies in the plotting technique. In thefirst method every recorded sample is included in a histogram and theresulting distribution is evaluated. Dominance of thermal noise and shotnoise would predict a Gaussian distribution [58]. The second methodwas proposed by Allan [59] in 1966. He provided a method capable todiscriminate and quantify different types of dominating noise sourcesover different time frames.

Present industrial standards for alcohol interlocks [39, 40] set de-mands on the ability to differentiate between various substances, bothfrom physiologically endogenous and environmental origin. Selectivity

3.2 Investigations of sensor performance 37

Figure 3.1: Chamber used for calibration of prototypes.

studies were therefore performed. Carefully measured IR-spectra for thesubstances of interest are publicly available [1] and allowed for calcula-tions based on actual sensor parameters. The method has previouslybeen published for our sensor system [60]. The most critical substanceshave also been experimentally determined by laboratory experimentsusing the previously described calibration set up.

Humans are the intended end user of the sensors and the sensors areaimed at measuring directly in human exhalation. The main compo-nents of human exhalation are N2, O2, H2O and CO2 [61]. To recreatethis gas mixture in a laboratory setting, pressurized gas, containing thedry gases, is bubbled through water at a flow aimed at mimiking human


Figure 3.2: Humid gas generator used to simulate a human exhalation.

exhalations, Figure 3.2. By adding ethanol to the water, the generatedoutput gas mixture resembles an exhalation by an intoxicated human.The water/ethanol tank is tempered to 34◦C, again to resemble humanexhalations. The system relies on Henry’s law [62] and is therefore lim-ited by the accuracy of the temperature regulation. Commercially avail-able breath alcohol analysers are calibrated using wet gas generatorsbased on a similar set-up and carefully prepared water/ethanol mixtures[63, 64, 65]. The gas pulse generator set-up was used to evaluate thetechnical accuracy and precision of the sensor. Pairwise measurementswere used for the evaluation. For each measurement by the sensor ameasurement was also made in a reference instrument. The reference in-

3.3 Human subject studies 39

strument used in the studies, called Evidenzer and is built by NanopulsAB, Sweden [66], is capable of measuring CO2, H2O and ethanol. Themeasured accuracy and precision were compared to existing industrialstandards [39, 40]. The experimental set-up was also used to investigatethe sensor response at various distance from the gas pulse exhaust to thesensor inlet.

3.3 Human subject studies

Figure 3.3: Human subject performing a breath test into a hand helddevice.

Exploratory studies were made using human subjects, Figure 4.3. Theaim of the human subject study was to gain vital knowledge of the mea-surement method and to validate the newly designed technology. Foreach measurement set performed by a human subject and recorded bya prototype, a reference breath test was also performed in an evidential


standard breath alcohol analyser. The instrument used as a reference inthe studies, called Evidenzer and is built by Nanopuls AB, Sweden [66],is capable of measuring CO2, H2O and ethanol. In many applications, abreath alcohol analyser is used as a classifier, i.e. below a certain out-put value the device shall remain in an unlocking state and above thatvalue the device shall remain in a locking state. The recorded data wastherefore treated as such. In real world applications high quality alcoholanalysers are regulated by industrial standards [39, 40, 67, 68, 69]. Listedrequirements and demands in said standards were also carefully consid-ered during data analysis. The measurement set-up employed duringthe human subject studies allowed for influence from the tracer gas, i.e.CO2, and a certain degree of freedom regarding exhalation technique.

The data recorded during the human subjects test was also used toinvestigate improvement possibilities to reduce known sources of vari-ation. Two different methods were evaluated and compared to a ba-sic calculation, both reducing variation caused by the use of a tracergas. The methods are complementary in the sense that one reducesvariation caused by inter-individual dissimilarity, and the other fromintra-individual divergence. The basic calculations include the assumedexpired CO2 constant, the measured CO2 concentration at the sensorlocation, the background CO2 concentration and the measured EtOHconcentration. Equation 3.2 shows the calculation.

BrAC =CO2exp − CO2bgrCO2meas − CO2bgrEtOHmeas (3.2)

The first method, equation 3.3, aims at reducing the variation causedby the use of a tracer gas. The calculation is dynamic in the sense thatlower measured dilution weighs higher towards an undiluted sample.

BrAC =1

DF∗ EtOHmeas + (1− 1

DF) ∗BrAC (3.3)

In the second method employs personalization to the assumed expiredCO2 constant according to equation 3.4.

BrAC = EtOHmeas ∗DF = EtOHmeas ∗ CO2expInd − CO2backgroundCO2meas − CO2background

(3.4)

The methods were evaluated individually as well as combined.

3.4 In-vehicle investigations 41

3.3.1 Note on ethics in relation to the human subjectstudies

Alcohol has a negative effect on the human body, both in the long andshort perspective, and can be considered a drug or a poison [11]. It istherefore of utter importance to inform recruited test subjects beforetesting is commenced to establish their informed consent. The humansubject study included in this work was approved by the Swedish Eth-ical Review Board in Uppsala (Dnr 2013/089). After performed test,transportation was arranged to ensure a safe journey home.

There are also obvious ethical aspects related to the effects of al-cohol on human health and driving. By extension these aspects havesocio-economic impact. Such considerations are extremely important.However, they are outside the scope of these studies.

3.4 In-vehicle investigations

Introductory tests towards integration of the sensors inside the vehi-cle compartment have been performed. Sensors were placed at differentdiscrete positions in close proximity of the driver seat. Sober human sub-jects entered the vehicle with the instruction to either breathe throughthe nose or the mouth. From the observed CO2 concentrations the di-lution of the gas sample was calculated. The sensors noise floor alsodecided the lowest detectable ethanol concentration. Based on these twoobservations, the feasibility to detect various intoxication levels could bededuced. In-vehicle experiments took place in a stationary vehicle insidea garage. The vehicle used for the studies is shown i Figure 3.4.

In a similar study, a sensor was integrated into the steering columnof the vehicle shown in figure 3.4. The installation is shown in figure 3.5.The aim of the study was to investigate the methodology of placing a sen-sor on a discrete position inside the vehicle compartment and passivelyevaluate the driver’s intoxication level. Without breathing instructions,subjects entered the vehicle and performed a simulated driving task forten minutes. During this time period sensor signals were logged andanalysed off-line after completion of the test. CO2 was again used toevaluate the quality of the samples reaching the sensor. Both sober andintoxicated subjects were used in the study. Video data was recordedduring the entire procedure. The use of a camera in relation to unob-trusive breath alcohol testing may increase the reliability and possibly


Figure 3.4: Vehicle used for in-vehicle experiments shown at an exhibi-tion in conjunction with the ESV conference in Gothenburg, 8-11 June2015.

accuracy of the measurement. The data recording is a first step towardscamera assisted alcohol detection.

The use of human subjects in testing is time consuming and ex-pensive. Therefore, two different standardized testing procedures forin-vehicle testing have been developed, depicted in figure 3.6.

The first method is based on the humid gas generator, figure 3.2. Thenew system includes three separate water/ethanol tanks, four heatedoutlet hoses and four outlet mouthpieces capable of switching betweensimulated mouth exhalations and simulated nose exhalations. The sys-tem is controllable via PC-interface and enables automated testing.

The second method is a computer simulation model built using Ansyssoftware. The use of simulations gives fast initial results to complexquestions. Simulation results is always directly related to the uncertaintyof the input parameters and is in need of validation. The two techniques,i.e. gas pulse system and simulation, are complementary to each otherand were used in combination to support the results.


Figure 3.5: Breath alcohol sensor integrated into the steering columncover.

(a) (b)

Figure 3.6: a) Experimental setup for in-vehicle testing of gas pulses. b)Simulation of in-vehicle breath distribution.

Chapter 4

Results

4.1 Investigations of sensor performance

In paper A the performance a new generation of IR-based alcohol sen-sor was characterized and evaluated. The sensor was found to meetthe performance requirements needed to enable breath alcohol screeningapplications. The investigated parameters were noise based resolution,sensor to sensor sensitivity variation, response time and specificity. TheRMS noise was measured to 0.0009 mg/L when allowing one second in-tegration time, Figure 4.1, far below the Swedish concentration limit of0.1 mg/L.

The 3σ sensitivity variation between different sensor prototypes wasfound to be less 10% before calibration. Further investigations showeda sensor response time of less than 0.5 s for both CO2 and ethanol. Thesensor also fulfilled the European standard for alcohol interlocks [39, 40]with regards to specificity. The feasibility to utilize the sensor for distantbreath alcohol, i.e. to use CO2 to account for the dilution of the sample,determination was also demonstrated.

To add to the sensor investigations, experimental bench tests arepresented in paper B and related to said standards [39, 40]. Amongstinitial experiments, four prototypes underwent functional testing withartificial gas pulses. In total 97 gas pulses containing 0.1 mg/L ethanolwere recorded. In the function tests the prototypes measured at a dis-tance with CO2 as the tracer gas to account for the dilution of thesample. The observed results were compared to a reference instrument

45

46 Chapter 4. Results

Figure 4.1: The resolution of the sensor at different time frames wasdeduced by the use of Allan deviation. At 1 second integration time,approximately the time of a human exhalation, the resolution of thesensor was determined to 0.0009 mg/L.

(Evidenzer, Nanopuls AB). All measurements were within 0.02 mg/L,the allowable error as listed in existing standards [39, 40] centred around0.1 mg/L

Bench testing with gas pulses was again used in paper F to investigatesensor performance at increasing distance between the gas exhaust andthe sensor inlet. Based on the measured dilution factor, the variationwas found to increase with increasing distance. The effect was found tobe most profound at distances above 30 cm. With a nominal alcoholconcentration of 0.3 mg/L, the sensor was able to distinguish gas pulsescontaining alcohol compared to gas pulses without alcohol at distancesup to 25 cm. Results from the tests are given in figure 4.2.

4.2 Human subjects studies 47

(a) (b)

Figure 4.2: a) Measured dilution factor at increasing distance. b) Mea-sured alcohol at increasing distance.

4.2 Human subjects studies

The main focus of paper B was a carefully controlled human subjectsstudy, including 30 human subjects. The new breath alcohol analyzerwas the test object and the resulting output are discussed in relation toaccuracy demands and requirements set by current industrial standards[39, 40].

In the human subjects study, the subjects were told to deliver breathsamples at three different distances, approximately 15 cm, approximately3 cm and with a mouthpiece. The measured data is shown in Figure4.3. The measurement variation increased at increasing distance. Nomeasured data point was classified as a false positive or a false nega-tive for undiluted tests or tests performed at the shorter distance. Thestatement is true when considering an allowable error band around theSwedish limit for drunk driving, derived from European standards for al-cohol interlocks [39, 40]. One measurement was determined to be falselyclassified at tests performed at a distance of approximately 15 cm andsaid concentration limit. When utilizing this analysis method to the Eu-ropean concentration limit, set at 0.25 mg/L, false positives and falsenegatives were found in tests performed at both 3 cm and 15 cm at afrequency of 1.7 %.


Figure 4.3: Results from a human subjects study. Both panels show thedata evaluated as a classifier with an allowed tolerance interval set for aspecified cut off value. The upper panel shows the results in relation tothe Swedish limit at 0.1 mg/L and the relation is made to the Europeanlimit at 0.25 mg/L in the lower panel.

The aim of paper D is improved algorithms addressing the variationintroduced by the methodology of contact free breath alcohol determi-nation. The paper is a result of better understanding of the technologyand physiological aspects of the methodology. Two possible method-ological improvements were investigated individually, together with thecombination of the two. Altogether, the observed variation was reducedby up to 40 %.

As a baseline, a noise reduction algorithm was used. To accountfor measurement variation caused by inter-individual CO2 differences inend tidal expiratory concentration, personalized normalization factorswere used. The method provided reduced random error by 28 %. Intra-


individual variation was countered by weighing the measured BrAC withthe measured ethanol value. The method showed a reduced variation of24 %. A combination of all three algorithms showed a reduction inrandom error of 40 %, Figure 4.4.

Figure 4.4: Left: Sensor output without any modifications made to themeasurement algorithm. Right: Sensor output with the two method-ological improvements implemented.

4.3 In-vehicle investigations

In-vehicle investigations was conducted with both FEM simulations onbreath gas flow and experimental measurements. Several sensor positionswere evaluated. Based on sensor resolution and breath dilution the mostfeasible position was concluded to be the seat belt position.

In the in-vehicle experiments human subjects were made to enterthe vehicle and control their breathing either through the nose or themouth. Several sensors were mounted inside the vehicle at various sensorpositions. The measured CO2 concentration was used to evaluate thedilution of the sampled gas. The most favourable position to measuregas originating from the nose was found to be situated at the seat belt.More surprisingly, this position also proved to be the most favourable


for mouth breathing as well, however together with a sensor located atthe sun screen, Figure 4.5.

Derived from expected ethanol concentrations at various dilutionsand measurements at 0 mg/L an indication of allowed maximum dilutionwas estimated to 20-30.

Figure 4.5: Dilution measured at various sensor positions inside the ve-hicle compartment. The blue, red and black lines show the concentrationof alcohol in a diluted breath sample based on the intoxication level.

Paper E is investigating completely passive breath alcohol determi-nation in a vehicle environment. The IR-based sensor was installed inthe steering column of a vehicle and human subjects were used for theinvestigation. In total 10 human subjects took part in the study, outof which 7 were sober and 3 were intoxicated. Each subject entered thevehicle and performed a task resembling driving for 10 minutes. Duringthis time period vital sensor signals, particularly CO2 and EtOH, wererecorded. The number of peaks and the magnitude of the peak were


then evaluated.The recording in figure 4.6 shows the measured CO2 and EtOH con-

centrations from an intoxicated subject. In the upper graph five clearlydistinctive CO2 peaks are visible. Time correlated peaks are also foundin the EtOH signal, lower graph. The signal response to EtOH gas ishowever covered in noise. The most important conclusion from the studywas that given enough time, passive breath alcohol may be feasible. Inorder to achieve that goal, the sensor resolution needs improvement byroughly a factor of 10-20.

Figure 4.6: Signals measured from an intoxicated subject. Upper graph:CO2 concentration increase. Lower graph: Ethanol concentration in-crease.

Paper F is also focused on passive detection of breath alcohol. Pre-vious investigations are mainly focusing on initial testing using humansubjects. This paper is introducing several techniques to standardizetesting. These include simulation, in-vehicle gas pulse generation andmapping of distance dependence. The paper also revisits the conclusionsfrom paper E, i.e. there is a need for increased sensor resolution in or-der for passive breath alcohol determination to be operational, with newinvestigative data including high resolution CO2 sensors. Further, thefirst steps toward camera assisted breath alcohol detection were made.

The results from simulation and in-vehicle gas pulses were in goodagreement, figure 4.7. The magnitude of the simulated and measured


gas concentration gas was also good agreement with the results from thehuman subjects studies presented in paper E. All three methods give theresult that the resolution of the sensor needs to be increased by a factorof 10-20 in order for passive breath alcohol determination to be feasible infield operation. The high resolution CO2 sensor provided evidence thatimproving the resolution of the sensor provides an increased possibilityto detect peaks fast and the ability to quantify them. This should beapplicable to any IR-active gas, including ethanol.

Image analysis was applied to extract driver behaviour data, such ashead positioning and direction as well as mouth opening. This part ofthe paper showed a promising start to fuse extracted data with sensordata to improve detection reliability and detection of non-conformingbehaviour.

(a) (b)

Figure 4.7: a) Simulated breath-by-breath recording of alcohol (lower)and CO2 (upper) concentrations. b) Experimental recording of in-vehiclesensor signals using gas pulses from the setup depicted in figure 3.6, CO2(top graph) and alcohol (bottom graph).

Chapter 5

Discussion

The aim of this work was to investigate a new generation of IR-basedbreath alcohol sensor designed and developed for measuring diluted hu-man exhalations. The results provide experimental evidence of sufficientperformance for screening applications at a short to moderate distancebetween the sensor and the mouth. The variations caused by physio-logical parameters can also be reduced by alternative calculation routes.A path to a passive system for in-vehicle use has also been proposed.Given enough time exhalations, from the driver will be detected. Like-wise, given enough resolution, classification of breath alcohol will bepossible.

Mouthpiece-free operation set higher requirements on sensor perfor-mance compared to undiluted testing. As the distance between themouth and the sensor increase, the concentration of the analyzed gasdecrease. To compensate for the concentration loss the resolution of thesensor needs to be improved by the same amount. Laboratory investi-gations showed the sensor resolution to be 1% of the Swedish limit fordriving under the influence of alcohol, allowing for dilution of the breathsample. The operating method of the sensors requires the use of a tracergas for estimating breath dilution. In doing so, variation from two gasmeasurements will influence the end result. The gases need to be mea-sured simultaneously and preferably in the same gas volume. Bench testexperiments showed similar time sequence between the two gases whenmeasuring both an undiluted sample and at a distance. Further benchtesting determined the maximum distance between the sensor and the

53

54 Chapter 5. Discussion

mouth to approximately 20 cm, corresponding to a dilution of 10. All to-gether, the sensor performance was found to meet the requirements forscreening applications with regards to accuracy, resolution, selectivityand response time.

In screening applications, it is of the essence to detect whether al-cohol is involved or not and to do so as quickly and easily as possible.The question is whether alcohol is present in the test subjects body ornot. The statement can be related to the risk increase associated withalcohol intoxication. The risk increase is higher at higher levels of alco-hol in the body, but the body will be affected negatively starting fromvery low concentrations [2]. The most important feature of a screen-ing instrument is to be able to correctly and reliably classify exhalationscontaining alcohol from those that lack alcohol. Using the data collectedduring the human subjects study, the sensor performance was investi-gated in combination with the methodology of using CO2 as a tracergas. In the European industrial standard for alcohol interlock a func-tional test is provided, which states an allowable error band around thelegal threshold for driving under the the influence of alcohol. It shouldbe noted that in the standard, the test is designed to be performed ina laboratory setting using gas pulses, i.e. without physiological errorsources. Different countries apply different limits for the legal thresh-old. The classifier analysis was therefore carried out at both the Swedishand the central European threshold concentrations. No falsely classifiedmeasurements were found around the Swedish limit. At the central Eu-ropean threshold 98.3% proved to be correctly classified. The resultsindicated that an instrument using the sensor in combination with CO2as a tracer gas allow for rapid screening of breath alcohol.

The physiological error sources associated with CO2 as a tracer gascan be divided into inter-individual and intra-individual variation. Atypical inter-individual source of variation is the end tidal CO2 concen-tration, ranging from 2.6 to 5 kPa [46]. By personalizing the normaliza-tion factor in the dilution factor calculation this type of variation couldbe reduced by approximately 25%. Intra-individual variation using themethod is more related to the breathing pattern and behaviour of thetest subject, i.e. a shallow exhalation will not provide as high exhaledCO2 concentration as an extended one. The source of variation wasaddressed by weighting the BrAC calculation to the level of dilution.A highly diluted breath relies heavily on the normalization calculation,while a close to undiluted breath disregard the normalization to great

55

extent. The result showed a variation reduction of approximately 25%.Using a combination of the two techniques reduced the impact of physi-ological error sources up to 40%. An instrument employing the proposedtechniques will gain more reliable classification when testing at low tomoderate dilution.

In more demanding situation, e.g. breath alcohol determination forevidential purposes, even higher accuracy and precision may be required.The human subjects study showed that the same sensor could exceed therequired performance for such situations simply by adding a mouthpiecefor undiluted operation. In some situations a two step procedure, usingthe existing technology may provide the combination of high throughputand high accuracy in the same instrument.

Measurement situations can be demanding in other ways than highaccuracy and precision. In a vehicle environment, passive detection ofthe drivers breath alcohol concentration would vastly improve the chanceof mass deployment of such technology. The technical challenges aresignificant, but so is the potential reward to save thousands of lives an-nually in the U.S. alone. Using experiments with human subjects andby placing sensors at a carefully selected location in close proximity ofthe driver, gas originating from the driver was shown reach the sensor.The concentration of the detected peaks were low and thereby settingextremely high requirements on sensor resolution. The sensor needs tobe able to measure gas diluted by a factor of 100-200. A driver witha breath alcohol concentration of 0.4 mg/L, i.e the legal limit in theU.S., would in this case produce gas for analysis at the sensor locationof 0.004-0.002 mg/L. At a given dilution there is a linear relationshipbetween driver intoxication the concentration recorded at the sensor lo-cation. The higher level of intoxication of the driver the easier it is todetect by the sensor. Coincidently, based on crash risk studies, the mostdangerous drivers are the ones with high level of intoxication [2]. Res-olution is but one challenge associated with passive alcohol detection.Time to detection is another. Without any active assistive technology,the method relies on an exhalation to be accidentally directed towardsthe sensor. In the investigations shown here, the time between detectedpeaks was a few minutes. There was also large variation between in-dividuals in terms of time to detection. In a real world environment adriver can not be prevented from driving for several minutes before anapproved exhalation has reached the sensor. The sober driver should notbe inconvenienced. A system based on the method may allow all drivers

56 Chapter 5. Discussion

to start the vehicle as usual and start diving. If alcohol is detected on alater occasion, the sensor may inform the driver of a less than preferabledriving state has been detected. The system may also limit the engineoutput in a safe manner.

Chapter 6

Conclusions

The work has resulted in the following three conclusions:

• The results provide experimental evidence of sufficient sensor per-formance for screening applications at a short to moderate distancebetween the sensor and the mouth.

• The variations caused by physiological parameters can be signifi-cantly reduced by alternative calculation routes.

• Given enough time, exhalations from the driver can be detectedpassivly at the sensor location without active cooperation of thedriver. Given enough resolution, classification of the driver breathalcohol content will be possible. There is however still a lot of workto be done before such a system may become available.

57

Chapter 7

Future work

Ease-of-use is the main parameter for successful unobtrusive breath al-cohol detection. One possibility to achieve easy-of-use is to allow forhigher dilution. In a more diluted breath sample, the concentration ofthe analysed gas is lower. In turn, the lower concentration sets highrequirement on the resolution of the sensor. Future work that leadsto high resolution is essential for unobtrusive breath alcohol detection.The next generation of sensors may include more sensitive and powerfuloptical components.

In vehicle applications, the mode of operation have many unansweredquestions, e.g environmental effects, maximum affordable time to detec-tion, etc. Investigations to collect vital field operational data is requiredfor understanding of the real world measurement situation. Data col-lected during such trials may result in smarter algorithms and sensorregulation.

The investigated sensor technology may provide the core informationsource in a system designed for passive detection of driver intoxication.However, in driver risk detection, auxiliary sensors may improve thechance of detection or even provide a first risk estimate on an earlystate. The initial estimate may be updated over time as more and moredata is collected. Studies including auxiliary sensors is planned to thenear future.

Other spectroscopic techniques have also shown to exhibit extremelyhigh resolution, e.g. mass spectroscopy [70] or laser based spectroscopy[71]. These would require miniaturization steps for possible integra-

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60 Chapter 7. Future work

tion in various screening applications. Other possibilities may lie in al-ready miniaturized techniques, e.g. optogalvanic spectroscopy [72]. Suchmethods needs to be investigated for sensitivity, stability and resolutionreasons.

Other substances can also be present in human breath, both of en-dogenous and exogenous origin. Amongst such substance, possible biomark-ers of disease [73, 74], and various narcotics [75], have been reported.The concentration of these substances are low in human exhalation andincreased resolution would be required for an easy to use instrumentcapable of drug or biomarker detection.

Bibliography

[1] Pacific Northwest National Laboratory. Vapor phase infrared spec-tral library. https://secure2.pnl.gov/nsd/nsd.nsf/Welcome, 2015.[Online; accessed 01-Sept-2015].

[2] R D Blomberg, R C Peck, M Burns, and D Fiorentino. Crash riskof alcohol involved driving: A case-control study. Technical report,Dunlap & Associates Inc., Stamford CT, 2005.

[3] B Saxton. Road traffic injuries 2012. Technical report, Swedish Gov-ernmental Agency Transport Analysis, Linköping, Sweden, 2013.

[4] M Melkersson and S Bengtsson. Road traffic injuries 2016. Tech-nical report, Swedish Governmental Agency Transport Analysis,Linköping, Sweden, 2017.

[5] National Center for Statistics and Analysis. Alcohol-impaired driv-ing: 2015 data. Technical report, National Highway Traffic SafetyAdministration, Washington DC, 2016.

[6] B Hök, H Pettersson, and G Andersson. Contactless measurementof breath alcohol. In Micro Structure Workshop, 2006.

[7] A Kaisdotter Andersson. Improved Breath Alcohol Analysis withuse of Carbon Dioxide as the Tracer Gas. PhD thesis, MälardalenUniversity, Väster̊as, Sweden, 2010.

[8] A Zaouk, M Willis, E Traube, and R Strassburger. Driver alcoholdetection system for safety - a status update. In The 24th Interna-tional Technical Conference on the Enhanched Safety of Vehicles,2015.

61

62 Bibliography

[9] B. Ver Steeg T. Ridder and B. Laaksonen. Comparison of spec-troscopically measured tissue alcohol concentration to blood andbreath alcohol measurements. Journal of Biomedical Optics, 14,2009.

[10] B. Ver Steeg T. Ridder, E. Hull and B. Laaksonen. Comparison ofspectroscopically measured finger and forearm tissue ethanol con-centration to blood and breath alcohol measurements. Journal ofBiomedical Optics, 16, 2011.

[11] J C Gariott. Garriott’s Medicolegal Aspects of Alcohol. Lawyers &Judges Publishing Company, Tucson AZ, 5 edition, 2008.

[12] G Liljestrand and P Linde. Uber die ausscheidung des alkohols mitder expirationsluft. Skandinavisches Archiv fur Physiologie, 80:273–298, 1930.

[13] R F Borkenstein and H W Smith. The breathalyzer and its appli-cations. Med. Sci Law, 2:13–22, 1961.

[14] R F Borkenstein. The role of the drinking driver in traffic accidents.Indiana University, 1964.

[15] J G Wagner, P K Wilkinson, A J Sedman, D R Kay, and D JWeidler. Elimination of alcohol from human blood. Journal ofPharmaceutical Sciences, 65, 1976.

[16] A W Jones. Physiological aspects of breath-alcohol measurement.Alcohol, Drugs and Driving, 6, 1990.

[17] M P Hlastala. The alcohol breath test—a review. Journal of AppliedPhysiology, 84, 1998.

[18] G Fox and J Hayward. Effect of hyperthermia on breath-alcoholanalysis. Journal of Forensic Science, 34, 1989.

[19] G Fox and J Hayward. Effect of hypothermia on breath-alcoholanalysis. Journal of Forensic Science, 32, 1987.

[20] A W Jones. Effects of temperature and humidity of inhaled air onthe concentration of ethanol in a man’s exhaled breath. ClinicalScience, 63, 1982.

Bibliography 63

[21] AW Jones and L Andersson. Comparision of ethanol concentrationsin venous blood and end-expiratory breath during a contraolleddrinking study. Forensic Science International, 132, 2003.

[22] M F Mason and K M Dubowski. Alcohol, traffic, and chemical test-ing in the united states: A résumé and some remaining problems.Clinical Chemistry, 20, 1974.

[23] A W Jones. Quantitative relationships among concentrations inblood, breath, saliva and urine during ethanol metabolism in man.In The 8th International Council on Alcohol, Drugs and TrafficSafety (ICADTS) Conference, June 1980.

[24] A W Jones. Road safety web publication no. 15. the relationshipbetween blood alcohol concentration (bac) and breath alcohol con-cnetration (brac): A review of the evidence. Technical report, De-partment of Transport, London, UK, 2010.

[25] J P Payne, D V Foster, D W Hill, and D G L Wood. Observationson interpretation of blood alcohol levels derived from analysis ofurine. Brithish Medical Journal, 3, 1967.

[26] Motorförarnas Helnykterhetsförbund. Test avalkomätare. http://www.mhf.se/sv-SE/sakrare-i-trafiken/bast-pa-alkolas-alkomatare/alkomatare/, 2017. [Online; accessed09-Aug-2017].

[27] National Highway Traffic Safety Administration. Highway SafetyPrograms; Conforming Products List of Screening devices To Mea-sure Alcohol in Bodily Fluids, 2012.

[28] National Highway Traffic Safety Administration. Highway SafetyPrograms; Conforming Products List of Evidential Breath AlcoholMeasurement Devices, 2012.

[29] K M Dubowski. The technology of breath-alcohol analysis. U.S.Department of health and human services, 1992.

[30] P Atkins and J de Paula. Atkins Physical Chemistry. Oxford Uni-versity Press, Oxford, United Kingdom, 8 edition, 2006.

[31] X Liu, S Cheng, H Liu, S Hu, D Zhang, and H Ning. A survey ongas sensing technology. Sensors, 12, 2012.

64 Bibliography

[32] A Kaisdotter Andersson, B Hök, D Rentsch, G Ruecker, and M Ek-ström. Improved breath alcohol analysis in patients with depressedconsciousness. Medical & Biological Engineering & Computing,48:1099–1105, 2011.

[33] A Kaisdotter Andersson, J Kron, M Castren, Å Muntlin Athlin,B Hök, and L Wiklund. Assessment of the breath alcohol concen-tration in emergency care patients with different level of conscious-ness. Scandinavian Journal of Trauma Resuscitation and Emer-gency Medicine, 23, 2015.

[34] A Kaisdotter Andersson, A Karlsson, H Pettersson, and B Hök.Unobtrusive breath testing. In The 20th International Council onAlcohol, Drugs and Traffic Safety (ICADTS) Conference, 2013.

[35] S Ferguson, E Traube, A Zaouk, and R Strassburger. Driver alcoholdetection system for safety (dadss) - a non-regulatory approach inthe development and deployment of vehicle safety technology to re-duce alcohol-impaired driving. In The 21th International TechnicalConference on the Enhanched Safety of Vehicles, 2009.

[36] S Ferguson, A Zaouk, N Dalal, C Strohl, E Traube, and R Strass-burger. Driver alcohol detection system for safety (dadss) - phase iprototype testing and findings. In The 22th International TechnicalConference on the Enhanched Safety of Vehicles, 2011.

[37] A Zaouk, M Willis, N Dalal, E Traube, and R Strassburger. Driveralcohol detection system for safety (dadss) - a status update. In The25th International Technical Conference on the Enhanched Safetyof Vehicles, 2017.

[38] D K Lambert, M E Myers, L Oberdier, M F sultan, C M Thrush,and T Li. Passive sensing of driver intoxication. In SAE WorldCongress, Apr 2006.

[39] European Committe for Electrotechnical Standardization. EuropeanStandard for Alcohol Interlocks – Test Methods and PerformanceRequirements. Part 1: Instrument for Drink-Driving-Offender Pro-grams, 2014.

Bibliography 65

[40] European Committe for Electrotechnical Standardization. Euro-pean Standard for Alcohol Interlocks – Test Methods and Perfor-mance Requirements. Part 2: Instruments having a Mouthpiece andMeasuring Breath Alcohol for General Preventive Use, 2014.

[41] A Jonsson, B Hök, L Andersson, and G Hedenstierna. Methodologyinvestigation of expirograms for enabling contact free breath alcoholanalysis. Journal of Breath Research, 3, 2009.

[42] L Lindberg, S Brauer, P Wollmer, L Goldberg, A W Jones, andS G Olsson. Breath alcohol concentration determined with a newanalyser using free exhalation predicts almost precisely the arte-rial blood alcohol concentration. Forensic Science International,168:200–207, 2006.

[43] A B Lumb. Nunn’s Applied Respiratory Physiology. Elsevier, 2006.

[44] M P Fitzgerald and J S Haldane. The normal alveolar carbonic acidpressure in man. Journal of Physiology, 32, 1905.

[45] K M Dubowski. Studies in breath-alcohol analysis: Biological fac-tors. Zeitung für Rechtsmedizine, 76, 1975.

[46] A Kaisdotter Andersson, B Hök, M Ekström, and G Hedenstierna.Influence from breathing pattern on alcohol and tracer gas ex-pirograms - implications for alcolock use. Forensic Science Interna-tionl, 206, 2011.

[47] M Folke. Measurements of Raspiratory Carbon Dioxide. PhD thesis,Mälardalen University, Väster̊as, Sweden, 2005.

[48] Global Monitoring Devision of the National Oceanic and Atmo-spheric Administration. Trends in atmospheric carbon dioxide;recent global CO2. https://www.esrl.noaa.gov/gmd/ccgg/trends/global.html, 2017. [Online; accessed 23-Aug-2017].

[49] M Apte, W Fisk, and J Daisey. Indoor carbon dioxide concnetra-tions and sbs in office workers. In Healthy Buildings 2000 Confer-ence, Aug 2000.

[50] Y Zhu, A Eiguren-Fernandez, W Hinds, and A Miguel. In-cabincommuter exposure to ultrafine particles on los angeles freeways.Environmental Science and Technology, 41, 2007.

66 Bibliography

[51] SJ rolls out national automated alcohol testing. http://www.railwaygazette.com/news/news/europe/single-view/view/

sj-rolls-out-national-automated-alcohol-testing.html, 2017.[Online; accessed 02-Oct-2017].

[52] S Albarda. Method and Apparatus Determining Alcohol Concetnra-tion in the Blood. US Patent No. 4,314,564. Assignee: DrägerwerkAG, Germany, 1979.

[53] D Grubb, A Frigyesi, M Finnhult, Daniel Dencker, S Olsson, andL Lindberg. Breath alcohol analysis by standardization to watervapour enables contact free sampling with preserved high accuracyand precision as compared with mouthpiece sampling. Journal ofForensic Investigation, 2, 2014.

[54] T Jonsson and L O Sjöström. Automatiska Nykterhetskontroller iSveriges Hamnar. http://mhf.se/client/files//content/Sakrare_i_trafiken/MHF_Rapport_alkobommar_Stockholm.pdf, 2015. [Online;accessed 20-Aug-2017].

[55] B Hök, H Pettersson, A Kaisdotter Andersson, S Haasl, andP Åkerlund. Breath analyzer for alocolocks and screening devices.IEEE Sensors Journal, 10, 2010.

[56] C Hummelg̊ard, I Bryntse, M Bryzgalov, J Henning, H Martin,M Norén, and H Rödjeg̊ard. Low-cost ndir based sensor platformfor sub-ppm gas detection. Urban Climate, 14, 2015.

[57] J U White. Long optical paths of large aperature. Journal of theOptical Society of America, 32:285–295, 1942.

[58] A van der Ziel. Solid State Physical Electronics. Prentice-Hall, Inc.,Englewood Cliffs, New Jersey, 2 edition, 2006.

[59] D W Allan. Statistics of atomic frequency standards. Proceedingsof the IEEE, 54:221–230, 1966.

[60] J Steggo, A Kaisdotter Andersson, and B Hök. Breath alcoholsensor for emergency care. In Proceedings in the Micronano SystemWorkshop, May 2010.

[61] W F Boron and E L Boulpaep. Medical Physiology. Elsevier Inc.,Pliadelphia PA, 2005.

Bibliography 67

[62] W Henry. Experiments on the quantity of gases absorbed by water,at different temperatures, and under different pressures. Philosoph-ical Transactions of the Royal Society of London, 93, 1803.

[63] K Dubowski. Breath-alcohol simulators: Scientific basis and actualperformance. Journal of Analytical Toxicology, 3, 1979.

[64] R Guth. Breath test simulator and method. United States Patent4,407,152, 1983.

[65] D Fisher and R Guth. Portable breath test simulator. United StatesPatent US 6,526,802 B1, 2003.

[66] M Fransson, AW Jones, and L Andersson. Laboratory evaluation ofa new evidential breath-alcohol analyser designed for mobile testing– the evidenzer. Journal of Medicine, Science and the Law, 45:61–70, 2005.

[67] Organisation Internationale de Métrologie Légale. InternationalRecommendation: Evidential Breath Analyzers, 2012.

[68] European Committe for Electrotechnical Standardization. Euro-pean Standard: Breath alcohol Test Devices Other Than Single UseDevices - Requirements and Test Methods, 2011.

[69] European Committe for Electrotechnical Standardization. BreathAlcohol Test Devices for General Public - Requirements and TestMethods, 2012.

[70] A Hansel, A Jordan, R Holzinger, P Prazeller, W Vogel, andW Lindinger. Proton transfer reaction mass spectrometry: on-linetrace gas analysis at ppb level. International Journal of Mass Spec-trometry and ion Processes, 149:609–619, 1995.

[71] J Mlynczak, J Kubicki, and K Kopczynski. Stand-off detection ofalcohol in car cabins. Journal of Applied Remote Sensing, 8, 2014.

[72] M Berglund. Miniature Plasma Sources for High-Precision Molec-ular Spectroscopy in Planetary Exploration. PhD thesis, UppsalaUniversity, Uppsala, Sweden, 2015.

[73] A Mashir and R A Dweik. Exhaled breath analytics: The new in-terface between medicine and engineering. Advanced Powder Tech-nology, 20:420–425, 2009.

[74] J Kwak and G Preti. Volatile disease biomarkers in breath: A cri-tique. Current Pharmaceutical Biotechnology, 12:1067–1074, 2011.

[75] O Beck, N Stephanson, S Sandquist, and J Franck. Detection ofdrugs of abuse in exhaled breath using a device for rapid collection:Comparision with plasma, urine and self-reporting in 47 drug users.Journal of Breath Research, 7, 2013.

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