[2000] Environmental Ergonomics

8/13/2019 [2000] Environmental Ergonomics

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* Tel.: # 44-01509-223023; fax: # 44-01509-223940. E-mail address: k.c.parsons @lboro.ac.uk (K.C. Parsons).

Applied Ergonomics 31 (2000) 581 } 594

Environmental ergonomics: a review of principles, methods andmodels

K.C. Parsons * Department of Human Sciences, Loughborough Uni versity, Loughborough, Leicestershire, LE11 3TU, UK

Received 1 June 2000; accepted 14 July 2000

Abstract

A review of the principles, methods and models used in environmental ergonomics is provided in terms of the e ! ects of heat andcold, vibration, noise and light on the health, comfort and performance of people. Environmental ergonomics is an integral part of thediscipline of ergonomics and should be viewed and practised from that perspective. Humans do not respond to the environment ina way monotonically related to direct measuresof the physical environment. There are human characteristics which determine humansensitivities and responses. Practical methods for assessing responses to individual environmental components are presented as well asresponses to &total ' environments and current and proposed International Standards concerned with the ergonomics of the physicalenvironment. 2000 Elsevier Science Ltd. All rights reserved.

Keywords: Environment; Ergonomics; Heat; Cold; Thermal; Noise; Vibration; Light; Health; Comfort; Performance

1. Introduction

Ergonomics can be de " ned as the application of know-ledge of human characteristics to the design of systems.People in systems operate within an environment andenvironmental ergonomics is concerned with how theyinteract with the environment from the perspective of ergonomics. Although there have been many studies,over hundreds of years, of human responses to the envi-ronment (light, noise, heat, cold, etc.) and much is known,it is only with the development of ergonomics as a disci-pline that the unique features of environmental ergonom-

ics are beginning to emerge. In principle, environmentalergonomics will encompass the social, psychological, cul-tural and organisational environments of systems, how-ever to date it has been viewed as concerned with theindividual components of the physical environment.Typ-ically, ergonomists have considered the environment ina mechanistic way in terms such as the lighting or noisesurvey rather than as an integral part of ergonomicsinvestigation. That is, for example, if cold distracts theworker then what are the consequences for the overallsystem? For a fuller description of the ergonomics

method the reader is referred to the paper by Wilson(2000) in this special issue. Environmental Ergonomicsmethods are described by Howarth (1995), Haslegrave(1995), Bonney (1995), Parsons (1985) and Parsons (1995).

The establishment of the study of human responses tothe physical environment has paradoxically inhibited thedevelopment of environmental ergonomics as it hasproduced associated institutions that provide inertia tothe acceptance of an ergonomics approach. Examplesinclude learned societies and conferences on speci " caspects of the environment, such as noise, lighting orvibration. The International Society for Environmental

Ergonomics"

rst met in Bristol in 1984 and has since thenheld successful biennial conferences around the globe.The original intention was to provide a forum for envir-onmental ergonomists, however it very soon becamespeci " cally concerned with human responses to heat andcold. In fact, it could be regarded as the forum for thatsubject. This provided a clear demonstration that thereare few researchers and institutions that consider humanresponses to environments as a whole, rather than interms of its component parts. The International Stan-dards Organisation (ISO) and more recently EuropeanStandards Organisation (CEN) have made signi " cant

contributions in the area of environmental ergonomics(see Appendix A). However, the existence of establishedstandards committees in noise, vibration, lighting and

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others has hampered progress as they often take a prod-uct- or manufacturer-orientated perspective which is nothuman centred and not conducive to an integrated ergo-nomics approach. This position is not static however,and it has become increasingly recognised that peopleexperience total environments and that ergonomicsmethods are essential for e ! ective practical application.Much knowledge exists, and new approaches will allowthat knowledge to contribute to environmental ergo-nomics as a major and essential contribution to ergo-nomics investigation.

There is a continuous and dynamic interaction be-tween people and their surroundings that producesphysiological and psychological strain on the person.This can lead to discomfort, annoyance, subtle and directa ! ects on performance and productivity, a ! ects on healthand safety, and death. Discomfort in o $ ces can be due toglare, noisy equipment, draughts, or smells. In the cold

people experience frostbite and die from hypothermia. Inthe heat they collapse or die from heat stroke. Peopleexposed to vibrating tools have damage to their hands.Performance can be dramatically a ! ected by loss of man-ual dexterity in the cold, noise interfering with speechcommunication or work time lost because the environ-ment is unacceptable or distracting. Accidents can occurdue to glare on displays, missed signals in a warm envi-ronment or disorientation due to exposure to extremeenvironments.

There are numerous factors that can make up a work-ing environment. These include noise, vibration, light,heat and cold, particulates in the air, gases, air pressures,gravity, etc. The applied ergonomist must consider howthese factors, in the integrated environment, will a ! ectthe human occupants. Three e ! ects are usually con-sidered; those on the health, comfort and performance of the occupants. The factors of the environment are usuallyconsidered separately. Some attempt at integration of e! ects can be made. However, there is insu $ cient objec-tive knowledge to allow an accurate quanti " cation.

This paper presents a review of the e ! ects of environ-ments on the health, comfort and performance of people

and of the principles upon which ergonomics assessmentsare made. The discussion will be con " ned to the factors of heat and cold, vibration, noise, and light. Other environ-mental factors and combined e ! ects will also brie # y beconsidered.

2. Environment and human response

Most of the energy that makes up our environmentoriginally comes as electromagnetic radiation from thesun. Around 1373 W m (the solar constant) enters the

outer limits of the earth 's atmosphere and this arrives onthe earth in modi " ed form where it is transformed fromplace to place and from one form to another (heat,

mechanical, light, chemical, electrical). The wide diversityof environments to which people are exposed are there-fore de " ned by that energy which varies in level, charac-teristic and form. It is the human condition to interactand survive in those environments and part of that hasbeen the creation of &local ' optimum environments (e.g.buildings).

The human body is not a passive system that respondsto an environmental input in a way that is monotonicallyrelated to the level of the physical stimulus. Any responsedepends upon a great number of factors. If viewed inengineering terms the &transducers ' of the body (sensors* eyes, ears, etc.) have their own speci " cation in terms of responses to di ! erent types of physical stimuli (e.g. theeyes have spectral sensitivity characteristics). In addition,the body does not behave as a passive system; forexample, the body responds to a change in environ-mental temperature by reacting in a way consistent with

maintaining internal body temperature (e.g. by sweatingto lose heat by evaporation). The body therefore sensesthe environment with a &transducer ' system that has itsown characteristics and it reacts in a dynamic way toenvironmental stimuli.

The above engineering model is simplistic. There aremany other factors involved. For example, the way inwhich a stimulus is perceived and hence any response toit will depend upon that person 's past experience, hisemotional state at the time and other factors. It is withconsideration of these physical, physiological and psy-chological factors that the environmental ergonomistmust provide a practical solution to the problems of howa human occupant will respond to an environment.

An additional factor that must be considered is that of individual di ! erences. These can be conveniently dividedinto inter-individual di ! erences that are di ! erences be-tween people (e.g. males and females, tall and shortpeople) and intra-individual di ! erences that are di ! er-ences that occur in the same person over time (e.g. emo-tional state, menstrual cycle changes in females). Thereare ways in which design can be made for speci " c indi-viduals. However, it is usual in practice to design for

a population of users. It is often adequate, therefore, todescribe individual di ! erences in terms of statisticalparameters of the population (e.g. mean and standarddeviation of responses).

3. Environmental ergonomics methods

There are four principal methods of assessing humanresponse to environments. These are: subjecti ve methods ;where those representative of the user population actual-ly report on the response to the environment; objecti ve

measures , where the occupant 's response is directlymeasured (e.g. body temperature, hearing ability, per-formance at a task); beha vioural methods ; where the

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behaviour of a person or group is observed and related toresponses to the environment (e.g. change posture, moveaway, switch on lights); and modelling methods . Model-ling methods include those where predictions of humanresponse are made from models that are based on experi-ence of human response in previously investigatedenvironments (empirical models) or rational models of human response to environments that attempt to simu-late the underlying system and hence can be used torelate cause and e ! ect.

Subjecti ve methods include the use of simple ratingscales, of thermal comfort for example, and more detailedresponses and questionnaires; they also include discourseanalysis and focus groups. They have the advantage of being relatively easy to carry out and are particularlysuited to assessing psychological responses such as com-fort and annoyance. They can also usefully be used whenthe contributing factors to a response are not known.

They have the disadvantage of being di$

cult to designhaving a number of potential methodological biases. Inaddition subjective methods are often not appropriate forassessing such things as e ! ects on health. For examplea person cannot always detect when he or she is undera great deal of physiological strain, also an environ-mental stress can interfere with a person 's capacity tomake a reliable subjective assessment. A further disad-vantage is that subjective methods often require the useof a representative sample of the user population beingexposed to the environment of interest. This is cumber-some if used in initial design.

Objecti ve methods have the advantage of providingdirect measures of human response. This could includemeasures of body temperature, transmitted accelerationto the head from vibration inputs for instance, as well asdirect measures of performance at a task. The maindisadvantages are that a representative sample of the userpopulation is required to be exposed to the environmentof interest (not useful for design), the measuring instru-ments can interfere with what they are intended tomeasure and objective measures cannot easily predictsubjective outcomes such as comfort.

Behavioural methods are probably underused in envir-onmental ergonomics. They can have the unique advant-

age of not interfering with what they are attempting tomeasure. They can include changes in posture, changingclothing, adjusting the environment, moving away, work-ing faster or slower, and so on. A requirement is thata &model ' is needed to interpret the &reason ' for anybehaviour. Observer training is required. These methodsare particularly suited for studying some peoplewith disabilities, children, or other special populations,or contexts where other methods would be inappropri-ate. A di $ culty is determining cause and e ! ect. Did

the person change posture because they were too hotor was the chair uncomfortable or the line of sightobscured?

Models of human response to environments have theadvantage of being consistent in their response, are easyto use, give a quick response and can be used in bothdesign and evaluation. The main disadvantages are thatthe models provide only approximate responses whendesigning for individuals and inevitably there will befactors in any real environment which the models do notconsider.

In most practical applications the ergonomist will usea combination of the methods as appropriate. Furtherdiscussion in this paper will focus on principles andmodels of human response to environments.

4. Environmental ergonomics models

4.1. Thermal en vironments and human response

There are six main factors that should be quanti"

ed inorder to assess human response to thermal environments;these are air temperature, radiant temperature, air velo-city, humidity, the activity of the occupants, and theclothing worn by the occupants. A thermal index inte-grates these values in a way that will provide a singlevalue that is related to the e ! ects on the occupants.

Humans are homeotherms * that means that they at-tempt to maintain their internal (core) temperaturewithin an optimum range (around 37 3C). If the body issubjected to thermal stress then the thermoregulatorysystem responds by changing its state in a way which isconsistent with maintaining core temperature within thisrange. This response of the body has consequences forthe health, comfort, and working e $ ciency of a person.

There are numerous indices that can be used to assessthe e ! ects of thermal environments on people. They canbe divided into three types. Empirical indices are thosewhich are derived from experiments. Subjects areexposed to a range of thermal environments and theirresponse is recorded. If a large range of thermal environ-ments is investigated a &model ' can be built up of humanresponse and this provides an index that can be used in&more realistic

' environments. A

&deri

ved

' index is basedon the value of a simple instrument that responds to the

factors in the thermal environment which also a ! ectpeople. The reading (e.g. temperature) of the instrumentprovides the index value. An example of this type of indexis the Wet Globe Temperature (WGT). This consists of a wet globe with a thermometer at its centre. The globeresponds to thermal radiation and air temperature and,because it is wet, the rate of evaporation (and cooling)will depend upon the relative humidity and air velocity.The derived indices do not always accurately &mimic 'human response to a given thermal environment; they

can however provide useful simple indices. Thermalmanikins are human-shaped &dummies ' (some heated,moving and sweating) that are used to determine the

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thermal properties of clothing and also to consider heattransfer across the body, which can be integrated intoa thermal index. The equivalent temperature index inte-grates temperatures across a thermal manikin to evaluatethermal comfort in vehicle environments.

Rational indices are derived from mathematical modelsthat describe the behaviour of the human body inthermal environments. If the body is to remain at ap-proximately a constant temperature then, on average, theheat outputs from the body must be equivalent to heatinputs to the body. This is known as heat balance anda usual starting point for derivation is the heat balanceequation

M ! = " E # R # C # K # S ,

where M is the energy produced by the metabolicprocesses of the body and W is the energy required forphysical work; C is the heat loss by convection; R is the

heat loss by radiation; K is the heat loss by conduction; E is the heat loss by evaporation; and S is the heat stored.By identifying the practical ways in which heat is ex-changed between the body and its environment, equa-tions can be derived and values of heat transfer can becalculated from the parameters measured in the physicalenvironment (air temperature, humidity, etc.). A numberof indices can then be derived, based on heat storage overtime or evaporation required for thermal balance, forexample.

Models for the assessment of thermal environmentshave moved beyond the thermal index to those thatrepresent the thermal properties of the human body (fat,muscle, skin, core, blood, covering head, trunk, arms,hands, legs, feet) with a model of human thermoregula-tion and heat transfer, in mathematical form. A computersimulation of the physiological responses to any environ-ment can be made. Predicted physiological responses canthen be related to the environmental e ! ects on health,comfort, and performance. Such models can, of course, beused in Computer Aided Environmental Design and As-sessment (Parsons, 1993).

4.2. Thermal environments

* health

When the body becomes &too hot ' or &too cold ' it reactsin a way that is consistent with maintaining core temper-ature at a relatively constant level. When the body isunder heat stress the two main mechanisms for losingheat are controlled by the anterior hypothalamus. Theinitial reaction is vasodilation, where the peripheralblood vessels dilate and transfer blood, and hence heat,to the surface of the body where it can be lost to thesurrounding environment. If core temperature continuesto rise, sweating occurs and considerable heat loss by

evaporation can occur. If these heat loss mechanisms areinsu $ cient to maintain heat balance then core temper-ature rises.

A practical approach to assessing the e ! ects of a heatstress on a worker is provided by a simple model used bythe World Health Organisation (WHO, 1969). Two re-gions are identi " ed, the prescriptive zone, where the bodycan maintain heat balance but is under some strain (dueto sweating, etc.) and the environmentally driven zonewhere heat balance cannot be maintained and body coretemperature rises.

A simple method of assessing an environment wouldbe to use a derived index; for example, ISO 7243 (1995)provides limiting values for thermal environments basedon the wet bulb globe temperature index (WBGT). Limitsare provided for a number of work rates for acclimatisedand non-acclimatised persons. A more detailed assess-ment can be provided using heat balance equations.Within the prescriptive zone the evaporation required(calculated from the heat balance equation) to maintainheat balance is a measure of the thermal strain on the

body and stress index with associated limiting values.The limiting values are usually based on the amount of sweat which can be produced by the body, the amount of water which the body can lose without dehydration, andthe amount of heat stored in the body (and hence themaximum acceptable rise in body core temperature). Inthe environmentally driven zone heat balance cannot bemaintained and allowable exposure times are calculated,usually based on a maximum allowable rise in body coretemperature. If the core temperature rises above &accept-able limits ' mental confusion can occur and death canrapidly follow. A maximum core temperature of 38 3C isoften used as a limit for working environments. Deathwill occur in the region of 42 3C core temperature. It maybe noted that, as well as heat stress, there are a number of heat disorders of the body which can be associated withexposure to hot environments. Heat disorders will not bediscussed in this paper and for further information thereader is referred to Leithead and Lind (1964) and Hub-bard and Armstrong (1986).

When the body is exposed to cold the two main mech-anisms for maintaining core temperature are controlledby the posterior hypothalamus. The initial reaction to

cold is vasoconstriction where peripheral blood vesselsconstrict and hence reduce the # ow of blood to the bodysurface that reduces heat loss. If body core temperaturecontinues to fall, additional heat is generated by shiver-ing. If body temperature still continues to fall mentalconfusion occurs, then unconsciousness, and " nallydeath due to ventricular " brillation (heart failure). Thereare a number of cold disorders (frostbite, trench foot,etc.), however they will not be considered in this paper.For further information the reader is referred to Burtonand Edholm (1955) and Hamlet (1988).

A practical approach to assessing the e ! ect of cold

stress on a workers ' health is to use, " rst of all, a simplederived index. The wind chill index (WCI) (Siple andPassel, 1945) can be used to integrate the e ! ects of air



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temperature and air velocity. The value provided canthen be used as a limiting value. Experience with theWCI has, however, been mainly in extreme outdoorenvironments and it may not be applicable in some &cold 'buildings. In refrigerated rooms it may be applicable;however, it was devised for outside (wind) conditions anda new index is required for cold stress. A more detailedassessment can be provided by use of a heat balanceequation. The strain on the body can be quanti " ed andclothing required to maintain heat balance can be pre-dicted. If clothing available is less than that required thenbody core temperature will fall and allowable exposuretimes can be calculated in terms of maximum fall in coretemperature.

4.3. Thermal en vironments * comfort

Thermal comfort can be de " ned as ` that condition of

mind which expresses satisfaction with the thermal envi-ronment a (ASHRAE, 1966). The reference to &mind ' indi-cates that it is essentially a subjective term; however,there has been extensive research in this area and a num-ber of indices exist which can be used to assess environ-ments for thermal comfort. Although simple values of airtemperature or globe temperature can be used to provideconditions for comfort in rooms a more detailed, practi-cal approach is usually taken.

Warmth discomfort has been shown to be related tothe &stickiness ' caused by un-evaporated sweat; forexample, trapped in clothing. Cold discomfort has beenshown to be related to the average skin temperature overthe body. That is, heat balance can be maintained (e.g. bysweating or vasoconstriction), however this is not a su $ -cient condition for comfort. Fanger (1970) suggestedthree conditions for comfort; these are that the body is inheat balance and that the mean skin temperature andsweat rate are within limits required for comfort. Condi-tions required for heat balance can be derived from a heatbalance equation. Mean skin temperatures and sweatrates that are acceptable for comfort have been derivedfrom empirical investigation (Fanger, 1970). A fourth

condition for comfort is that there should be no localdiscomfort. This could be caused by draughts, radiantasymmetry or temperature gradients.

A practical approach to assessing thermal environ-ments for the comfort of the occupants is provided byFanger (1970). An index (Predicted Mean Vote * PMV)predicts the mean vote, on a seven-point thermal sensa-tion scale, of a large group of occupants in the room. Thescale ranges from # 3 (corresponds to &hot ') through0 (corresponds to &neutral ' and is the value for comfort) to! 3 (corresponds to &cold ').

Individual di ! erences are &accounted for ' by providing

a method for predicting the percentage dissatis " ed (PPD)with the environment as a function of PMV values. ThePMV index is a widely used method for assessing thermal

comfort. There are a number of other thermal comfortindices and the standard e ! ective temperature (SET) hasbeen developed in the USA (Nishi and Gagge, 1977). TheSET is a complex index that can be used in heat and coldstress environments as well as for measuring thermalcomfort. The PMV index has been adopted as the Inter-national Standard method for assessing thermal comfort(ISO 7730, 1994).

4.4. Thermal en vironments * performance

Accurate predictions of the e ! ects of environments onperformance at a speci " c &real ' task are di $ cult to make.This is because there are many variables that relate tospeci " c tasks in speci " c contexts and all cannot be ac-counted for. However, using task analysis, components of tasks can be determined. General guidance can thenoften be provided from studies of similar tasks or studies

of similar task components. A simple example would bethe division of a task (or job) into mental and manualcomponents. The e ! ects of a given environment on sim-ilar mental tasks could be derived from previous studies;similarly for the manual task components. A useful over-all prediction can often then be made.

There have been numerous studies of the e ! ects of thermal environments on human performance and fordetailed reviews the reader is referred to McIntyre (1980);Fox (1967); Kobrick and Fine (1983) and Parsons (1993).The " ndings are often speci " c to the particular investiga-tion: however, a number of general conclusions can bemade. When the body is exposed to heat the e ! ects onperformance will depend upon a large number of vari-ables. An important consideration will be psychologicalparameters such as level of arousal and motivation aswell as other factors that contribute to individual di ! er-ences such as the degree of acclimatisation of the personto the environment. As heat stress increases there will bee! ects on mental performance. Wing (1965) and Ramsey(1995) investigated a wide range of mental tasks andpresent limits in terms of WBGT values that providegeneral guidance on exposure times within which there

would be no signi"

cant decrement in mental perfor-mance. Decrements in performance occur not only athigh environmental temperatures. Performance at vigi-lance tasks can be lowest in slightly warm environmentsthat can have sopori " c e! ects. An increase in environ-mental stress can then increase performance. In addition,as the rate of chemical reactions in the body increase withtemperature, a person 's speed at both physical and men-tal tasks can be increased (Poulton, 1976).

The e ! ects of cold on human performance are oftenignored and can be very signi " cant. While there are fewe! ects on mental performance cold can cause an increase

in arousal and improve performance at visual tasks. Inaddition, in more extreme environments, cold can actas a &secondary task ' hence increasing workload and



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possibly decreasing mental performance and if body coretemperature falls signi " cantly, mental confusion can oc-cur. The e ! ects of cold on manual performance can beattributed to physiological reactions to cold. The maine! ects are in slowing of speed, due to sti ! ening of jointsand slow muscular reaction, numbness, and a loss instrength. These reactions cause deterioration in manualdexterity and hence of performance at many manualtasks.

4.5. Vibration and human response

Vibration can signi " cantly a ! ect the health, comfortand performance of people, particularly in vehicles. A fullreview of the subject is provided in Gri $ n (1990). Thispaper can present only a summary and concentrates onhuman responses to the built environment. The study of human response to building vibration can be divided into

two areas: one area is concerned with the e!

ects of low-frequency (often large displacement) vibration(motion) that would occur at the top of tall buildings (dueto the buildings ' response to wind for example); the otherarea is concerned with vibration transmitted to buildingsfrom such things as road tra $ c, trains, or aircraft passingnearby or the operation of heavy machinery or blastingoperations, etc. This type of vibration has a relativelyhigh-frequency content and can have a di ! erent e ! ect onthe building occupants.

The e ! ect of vibration on building occupants will de-pend upon the characteristics of the vibration and thecontext in which the persons &receive ' the vibration. Thevibration is de " ned in terms of its level (usually acceler-ation) and frequency content. In addition it enters thebody in a number of directions (usually resolved intofore-and-aft ( x-axis), lateral ( y-axis) and longitudinal( z -axis)) which are de " ned in relation to the person (e.g.the z -axis vibration is from feet-to-head; if the person issitting or standing this is vertical vibration; if they arelying down it is fore-and-aft vibration, etc.). The vibra-tion can occur simultaneously in these three axes, ata number of input points to the body and can be of

varying duration. The environmental ergonomist re-quires a method of reducing this complex vibrationenvironment to a value that is related to the e ! ects onthe occupants of the building who are exposed to theenvironment. Taking account of personal characteristicsof those exposed with other contextual factors (typeof building, etc.) a prediction of likely e ! ects can bemade.

4.6. Vibration * health

There are levels of vibration that can cause physical

damage to the body; for example, those found in aircraftin severe turbulence, long-term exposure of tractor oper-ators to vibration, or vibration to the hand from some

vibrating tools. It is highly unlikely that the occupants of buildings would be exposed to vibration levels thatwould directly cause physical damage to the body.Methods by which building vibration can a ! ect healthare therefore indirect; causing a loss of balance in per-sons, for example, or simply as an additional environ-mental stressor that can a ! ect mental health andemotional state. In practice, it is di $ cult to providea model which will predict these e ! ects and subjective,objective and behavioural methods of investigation aremore appropriate.

4.7. Vibration * & comfort '

The term vibration discomfort is used in studies of human response to vibration. However, this relates moretowards the e ! ects of vibration on the occupants of vehicles and is not appropriate in the context of building

vibration. In practice, the building designer or transportsystem operator wish to know at what level of vibrationoccupants will be disturbed and complain. Whether oc-cupants complain about an environmental stress is high-ly context dependent and can be based on such factors asfear of building collapse or structural damage, the per-ceived source of vibration and the attitude of the occu-pant to the source. Accurate predictions are thereforedi$ cult to make for individuals, however general guid-ance can be provided for populations of occupants.

A practical approach to assessing human response tobuilding vibration is to assume that occupants will not bea ! ected by vibration that they cannot detect or feel. Thismay not be true in all applications and subliminal e ! ectsmay occur, however, it is a reasonable practical assump-tion. Predicted disturbance in buildings can then be re-lated to &absolute ' vibration perception thresholds.

Studies of human response to vibration in tall build-ings has been reviewed and a practical approach toassessment is provided in ISO 6897 (1984). This standardrelates to typical responses of people to horizontalmotion (of buildings) in the low-frequency range of 0.063 } 1.0 Hz. Two conditions are considered, of fre-

quently occurring vibrations and of infrequently occur-ring vibration such as experienced in the peak of a stormwhich has a " ve-year return period. Limiting curves of root-mean-square acceleration level against vibrationfrequency are provided. These apply to buildings used for&general purpose ' although guidance is provided, in termsof absolute perception thresholds, for buildings where anenvironment is required to be apparently stationary.Methods of measurement and analysis are provided togive a value (index) which is related to expected adversecomment about the vibration environment. It is im-portant to note, however, that this method excludes

perception of motion by related cues such as noise (orinfra-sound) associated with the motion or visual cuesobtained by looking out of windows.



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A similar but more detailed approach is taken whenassessing building vibration that is induced by, forexample, tra $ c passing near to a building, blasting op-erations, etc. A summary of research " ndings has led tothe practical method which is described in BS 6472(1984). This standard provides general guidance on hu-man exposure to building vibration in the frequencyrange 1.0 to 80.0Hz. Frequency weighting functions thatshow relative absolute perception threshold vibrationlevels over vibration frequency, are presented and theseare used to integrate e ! ects of vibration level, frequencyand axis into an &index ' value that can be used to deter-mine the e ! ects of impulsive vibration, intermittent vi-bration and continuous vibration on the occupants of buildings. The vibrations are measured at inputs to theoccupants of the building. Limiting values are providedin terms of building type (e.g. hospitals, residential,o$ ces, workshops, etc.) and time (day or night). The

limits are provided in terms of multiplying factors abovethe perception threshold levels (base curves). Forexample, limits for continuous vibration in o $ ces duringthe day are at four times the base curve values. If thelimiting levels of vibration in a building are not exceededthen the &prediction ' is that, with respect to &human re-sponse (annoyance, complaints) ' , they are at acceptablelevels.

The above methods provide only approximate assess-ments of building vibration environments and manypossibly important variables are not included. Inaddition, research into absolute vibration percep-tion thresholds has provided more extensive data(Parsons and Gri $ n, 1988). However, the methods pre-sented take some important human response to vibrationvariables into account and provide reasonable guidelineson which to assess human response to building environ-ments.

4.8. Vibration * performance

Vibration can have large e ! ects on human perfor-mance at simple tasks (e.g. reading, writing, drinking) and

many studies have shown major e!

ects on manual con-trol and vision. These e ! ects occur at levels found mainlyin vehicles and are unlikely to occur in buildings. Low-frequency vibrations often create large displacements intall buildings and can cause loss of orientation and bal-ance in subjects. However, these e ! ects have yet to bequanti " ed and their e ! ects on tasks (e.g. typing) cannotbe easily predicted. The method proposed in ISO 6897(1984) provides vibration limits for o ! shore " xed struc-tures where &tasks of a critical nature ' are being carriedout. However, these limits are based on only a limitedamount of relevant data. Building vibration may a ! ect

human performance, but little information exists. Vibra-tion can act as a general environmental stressor; but thisis di$ cult to quantify.

4.9. Noise ~ human response

The human ear detects sound pressure changes in theair and transmits a signal, which is related to the soundpressure changes, to the brain where it is perceived assound. The signal which is &perceived ' by the person is notdirectly proportional to the sound pressure stimuluswhich " rst entered the ear. There is a human perceptiontransfer function. For a given sound pressure level, forexample, a single frequency noise (pure tone) at onefrequency may sound &louder ' than a pure tone sound ata di ! erent frequency even though they are at the samephysical sound pressure levels. The relative e ! ect of sound frequency on loudness (for example) has beenquanti " ed in experimentation and &equal loudness con-tours ' have been produced. Based on &equal loudness(annoyance, noisiness, etc.) contours ' weighting functionshave been proposed which approximate the average per-

ceived response of a population. In practical applicationthese allow a physical stimulus (sound pressure level) tobe weighted in a way which approximates to the human&perceptual transfer function ' . The weighted noise levelscan then be used as the basis for an environmental indexfor noise. As the human ear can detect a wide range of sound pressure levels and because it was thought thata subjective scale of loudness was a logarithmic function,physical levels of noise are measured in decibels (dB(lin)).When the noise is modi " ed using a human perceptionweighting function then the resulting decibel level pro-vides a value that is related to human response. Forexample, an A-weighting curve is often used in practicalapplication and the resulting decibel level is called dB(A).

As well as level and frequency content of any noise animportant consideration is the duration of exposure.Duration must therefore be included in any environ-mental limits or guidelines for assessing human responseto noise. A method of including noise duration in anyassessment is to use the concept of equivalent continuoussound level ( L ). As noise levels typically vary overa working day L provides the level of continuous noisewhich, over the time period of interest, would cause the

same sound energy to be received as that due to theactual noise over the time period. If the noise is weightedwith an A-weighting, for example, then an index of thenoise e ! ective &dose ' of a person can be given by thedB(A) L value.

It must be noted that, although the principles forderiving an environmental index are as described above,there are many noise indices that are used in practiceaccording to the situation under investigation.

4.10. Noise ~ health

Noise can have direct and indirect e ! ects on workers 'health. Long-term exposure to noise causes noise-in-duced hearing loss. This is due to damage to sensors in



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the inner ear. The e ! ect is in terms of reduced sensitivityto certain frequencies of noise. Reduced sensitivity occursinitially, usually in the region of 4 kHz and, as the condi-tion becomes more severe, sensitivity is further reducedand this occurs over a broader frequency band. A practi-cal approach to assessing the noise health hazard is touse the index dB(A) L (Burns and Robinson, 1970).Limiting values of around 85 } 90 dB(A) L have beenproposed for 8 h exposure in industrial environments.

Indirect e ! ects on workers ' health could includephysiological responses (change in heart rate, blood pres-sure, adrenalin production, etc.). However, it is di $ cult torelate these changes directly to harmful e ! ects on thebody. Psychological responses to noise can also producee! ects on mental health and emotional state. especially if the noise adds to an already stressful environment. Inaddition, noise could a ! ect sleep in terms of both qualityand quantity. Indirect e ! ects of noise are often di $ cult to

demonstrate and also to quantify in practice. Guidelineson their e ! ects are therefore di $ cult to formulate. Sub- jective (or objective) methods may be more appropriatefor such assessments. Infrasound (low-frequency sound)can cause whole-body vibrations of the body, howeverlevels that would cause damage are very high and nor-mally this noise is perceived but is not directly harmful.

4.11. Noise ~ comfort

The term comfort is not usually used when assessingthe e ! ects of noise on the occupants of buildings. Inpractice, annoyance levels is the most useful criterion,although loudness, perceived noisiness, and nuisance arealso terms used. There are many indices that can be usedto provide a value that is related to ratings of the termsdescribed and no one index is generally used. HoweverdB(A) L is a widely used index. A simple practicalapproach to assessing noise in o $ ces, for example, wouldbe to measure the noise throughout the o $ ce and takethe average dB(A) value. If a more detailed analysis isrequired then the noise could be analysed in the fre-quency domain that would also help identify the causes

of the noise. A tra$

c noise index (TNI) has been pro-posed for predicting community response to tra $ c noise(Gri $ ths and Langdon, 1968). This is based on the con-cept of L10 and L90 which are measured in dB(A) and arethe noise levels exceeded for 10 and 90% of the time of interest, respectively. Other indices would include thenoise number index (HMSO, 1963) for assessing thee! ects of aircraft noise and 24 h dB(A) for railwaynoise (Fields and Walker, 1980). There has been a greatdeal of research in this area and a number of practicalapproaches to assessment exist. However, the lack of a common index for di ! erent situations can cause di $ -

culties. For example, if a building is exposed to road, rail,and air tra $ c, there is little guidance on which index ismost applicable.

4.12. Noise ~ performance

The e ! ects of noise on human physical and mentalperformance can be divided into e ! ects on non-auditorytask performance and e ! ects on auditory task perfor-mance (e.g. interference with speech communication,etc.). The e ! ects of noise on non-auditory taskperformance have been inconclusive, di ! erent studies in-dicating that noise reduces task performance, has noe! ect on task performance or increases task performance.No obvious general predictions can therefore be made.A major consideration appears to be the level of arousalof persons as compared with that required for optimumperformance at tasks. Performance at vigilance tasks, forexample, can be improved by increasing noise levels,hence increasing arousal to an optimum level. In practi-cal application the variation in results has not beensu $ ciently explained to allow accurate predictions of the

e!

ects of noise on the performance of the occupants of buildings. Some general predictions can be made, how-ever, based on models of human response to noise andprevious laboratory and " eld investigations.

Noise can interfere with auditory communication of information (speech, warning signals, etc.) and hence candecrease task performance. The human auditory systemcan detect signals within a background of noise. It isimportant to know the &e$ ciency ' of this detection withina speci " c type of background noise; for example, to beable to assess the e ! ects of background noise on speechcommunication or to design a warning signal for thatenvironment. The auditory system can be regarded asa set of " lters, which have bandwidths that depend uponnoise frequency, called &critical bands ' . The detectionthreshold of a signal within a background noise can berepresented as a signal-to-noise ratio over noise fre-quency. The detectability of a signal can then be cal-culated from the signal-to-noise (SIN) ratio within eachcritical band. (One-third octave bands are usually used inpractice.) Noise can mask speech and make it inaudibleor it can reduce its intelligibility. Criteria exist wherebythe interference e ! ect on speech can be quanti " ed in

terms of the distance between the speakers at whichvarious e ! ects on communication will occur (Miller,1974). A more exact quanti " cation is provided by inves-tigating the speech and background noise frequency con-tent. An environmental noise speech intelligibility indexcan then be used. There are a number of these indices.The articulation index (Kryter, 1970) for example, usesthe SIN ratio for each of 20 narrow bands, summation of e! ects within each band provides the articulation index.Values of the index are then related to e ! ects on varioustypes of speech.

As with other environmental stresses, noise can add to

the &overall workload ' in a given task and can potentiallya ! ect performance in this way. In addition, if a personis exposed to high-intensity noise the human auditory



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system reacts in a dynamic way and increases the thre-shold of the system. This temporary threshold shift canthen have an e ! ect on overall task performance after therelatively high-intensity noise has been reduced.

4.13. Light and human response

Light is that part of the electromagnetic spectrum thatis detected by the human eye. The eye is, however, notequally sensitive to all wavelengths of light and there isa human perception transfer function. This function de-pends upon the level of light present. For example, theeye is most sensitive to light at about 555 nm(green } yellow) under photopic ( &high- ' intensity) condi-tions and at about 505 nm (blue } green) in scotopic ( &low- 'intensity) conditions. Standard sensitivity curves areavailable and can be used in practical application(e.g. CIE, 1978). As light is by de " nition related to a

human observer, then the basic units used to specify lightare those for electromagnetic radiation weighted with thehuman visual system &weighting function ' . This is lumi-nous # ux. The properties of a lighting environment rel-evant to human response to it lead to other photometricunits that are related to luminous # ux. For example, theluminous # ux falling on the unit area of a surface is calledthe illuminance. Luminance is the luminous # ux emittedin a given direction per unit solid angle per unit surfacearea. Luminance is related to the brightness of an object.

The human eye does not behave passively to a lightstimulus. It reacts in a dynamic way. This allows a widerange of lighting levels to be received (adaptation) andconditioned (focussing, etc.). If the environment changesrelatively rapidly in lighting level then the dynamic re-sponse of the eye lags behind the change and can takefrom 2 min (light adaptation * cones) to 20 min (darkadaptation * rods) for it to adjust to the &new environ-ment ' . The spectral content of a light source will deter-mine the perceived colour of that source. The basicattributes of perceived colour are hue, brightness, andcolourfulness. Using concepts related to these attributes,colours can be classi " ed. There are also methods of

quantifying the colour appearance (e.g. correlatedcoloured temperature) and colour rendering properties(colour rendering index) of light sources (see Boyce,1981).

A consequence of the dynamic response of the eye toa change in light level is that when there is a wide range of luminances within a visual " eld, glare can occur. Thisdepends upon the luminance of a source compared withits background and its position within the angle of sightof the observer. Using these variables a glare constantcan be calculated for a single glare source and, if integ-rated over the visual " eld, this provides a glare index. It is

important to note that there are large individual di ! er-ences in human response to light. In addition, defectsoccur in the visual system (colour defects, myopia, etc.).

These will not be discussed in detail in this paper but it isimportant to identify the user population when designinglighting environments.

4.14. Light * health

Excessive exposure to light can cause direct e ! ects onhealth. Ultra violet, infrared, and visible radiation cancause health problems in the eye. In addition, this radi-ation can also damage skin. Limits above which damagewill occur have been quanti " ed (ACGIH, 1998). In addi-tion to these direct e ! ects on health, eyestrain can becaused by inadequate lighting conditions. Too little ortoo much light, veiling re # ections, disability, and discom-fort glare and # icker can all cause eyestrain (Boyce, 1981).This can cause irritation in the eyes, a breakdown of vision and headaches, indigestion, giddiness, etc. Thereare non-visual e ! ects of light on the body (e.g. light can

in#

uence the activity of glands, etc.); however, these aredi$ cult to quantify and not much is known about theire! ects. A practical approach would be to keep within thelimits of physical damage, by radiation to tissue (e.g.ACGIH (1998) and design &good ' lighting environmentsas recommended by CIBSE (1994) for example).

4.15. Light * comfort

Light can cause discomfort to the occupants of anenvironment as well as positive sensations such as pleas-ure and emotional sensations (cold, warm, etc.). Lightingconditions which produce de " nite discomfort can gener-ally be identi " ed and criteria in terms of physical lightingparameters are available for assessing lighting environ-ments (CIBSE, 1994). The conditions that create emo-tional responses or pleasant environments are not as wellunderstood and designing for these conditions remainsboth an art and a science. Lighting conditions that aresatisfactory are context dependent, depending upon thefunction of the building, user population, etc. However,there are a number of measurements of lighting environ-ments that are related to subjective responses to lighting

and recommended limits can be provided in terms of these parameters. For a detailed discussion the reader isreferred to Boyce (1981) and for practical recommenda-tions to CIBSE (1994). The parameters include il-luminance and illuminance ratios that are related to theacceptable light distribution arriving on surfaces ina room; Vector/scaler ratio and vector direction thata ! ect the three-dimensional appearance of objects; andmeasures of surface re # ections, colour, glare, anddaylighting can all be used to provide guidelines for goodlighting practice.

Human response to light is a very complex subject and,

despite a great deal of research, accurate predictions of subjective impressions are still di $ cult to make. How-ever, this area of human response to the environment has



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Table 1Summary of useful models

Health Comfort Performance

Heat ISO 7243 * limits in terms of WGBT index. ISO 7933 * required sweat rate to maintaincore temperature. Predicted heat strain.

Warmth discomfort is related tostickiness caused by sweat. ISO 7730provides Predicted Mean Vote (PMV)

WGBT limits for cognitive tasks (Ramsey,1995). Sopori " c e! ects of warmth decreasevigilance. Sweating a ! ects grip.

Cold Wind chill index and an index basedupon the required clothing insulationto maintain core temperature.

Cold discomfort is related to meanskin temperature. ISO 7730 providesPredicted Mean Vote (PMV).

Possible large e ! ects on skin sensitivity,manual dexterity, and strength (Fox, 1967).

Vibration No direct e ! ects in buildings. Usesubjective methods.

Limits based on vibration perceptionthresholds. ISO 6897 for low frequencyvibration, BS 6472 for 1 } 80 Hz vibration.

Limited data available for buildingvibration.

Noise Noise induced hearing loss in termsof dB(A) leq . Non-auditory e ! ectsdi$ cult to predict.

A number of indices for predictingannoyance etc, depending upon context.dB(A) is a useful general measure.

Non auditory e ! ects di $ cult to predict.

Light ACGIH (1998) * radiation limits for

physical damage to tissue. Eyestraincaused by many factors. CIBSE (1994)for good lighting practice.

Still art as well as science.

Subjective methods useful. CIBSE(1994) for good lighting practice.

CIBSE (1994) * for good lighting practice.

Size, contrast, luminance, colour,population age, visual defects etcare all important.

employed sophisticated psychophysical scaling tech-niques (e.g. multidimensional scaling) and it may be pos-sible in the future to provide more accurate models of subjective impressions of lighting environments.

4.16. Light * performance

Although light can a ! ect human performance at gen-eral tasks, glare can cause a distraction e ! ect; forexample, the main e ! ects of light are on visual perfor-mance. Visual performance is related to a combination of the e $ ciency of the eye in receiving and conditioninglight and the interpretation of what is seen by the person.While training can in # uence workers ' interpretation of what is seen, in practice lighting guidelines are requiredto provide the desired visual performance at particulartasks. For a detailed discussion of visual performance thereader should refer to Hopkinson and Collins (1970),

Boyce (1981), Megaw and Bellamy (1983), Megaw (1995)and Howarth (1995). Practical recommendations forworking environments are provided in CIBSE (1994).There are many parameters that will in # uence visualperformance and many of these are task-dependent.However, there are a number of parameters that are of general importance; these include the contrast betweenan object to be viewed and its background, and the size of the object. Other factors would include the luminance of the object and the time for which it is viewed. Manystudies have been conducted into the relative importanceof these variables on visual performance (e.g. visual acu-ity * ability to see " ne detail). The results of these studiescan provide guidance on optimum lighting conditions for

real tasks such as visual inspection. It is interesting that,as well as studies involving real tasks in external environ-ments, an analytical approach has also been taken, bydetermining visual perception thresholds; lighting speci-" cations for &real ' tasks were then related to these thre-sholds. In addition to the e ! ect of general illuminancelevels on visual performance, e ! ects can also occur due todisability glare, and veiling re # ections. Colour judge-ments are often also of importance in, for example, in-spection. Individual di ! erences in user reaction andcapability are important in design; for example, an agedpopulation may have a decreased visual e $ ciency. Theprovision of lighting for optimum user performance istherefore complex and task speci " c. However, practicalguidance is available (e.g. CIBSE, 1994) to enable a rea-sonable " nal approximation to these optimum conditions.

5. The &total

' environment

Although environments are usually assessed in termsof the e ! ects of their separate component parts (seeTable 1), occupants of buildings in practice are exposedto whole, &integrated ' environments. The design or assess-ment of total environments therefore involves both &maine! ects ' of environmental components as well as interac-tions of the components. How components of environ-ments interact has been the subject of a number of studiesbut only general guidance can be provided. Nevertheless,in practice, the ergonomist must consider the total envi-ronment, whether knowledge of its e ! ects is available ornot. General guidance on the e ! ects of &combined ' envir-



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onmental components can be obtained from underlyingmodels as well as results of empirical studies. Broadbent(1971) suggests that the e ! ects of combined stresses onpeople are arithmetically additive if the &internal mecha-nisms ' which they a ! ect are independent. However if the&internal ' mechanisms are not independent then the ef-fects can be additive or synergistic (the whole is greaterthan the sum of the parts) or subtractive. The arousalparadigm is often used in attempts to explain combinede! ects of environmental stressors; for example, loss of sleep will reduce arousal and may decrease performanceat a vigilance task, noise will increase arousal. Noise andloss of sleep combined will then maintain arousal andhence performance. Although the underlying model maybe simplistic, this idea can be used in practice (e.g. playmusic in a factory where vigilance (inspection) tasks arebeing carried out). An additional model that can be usedto predict the e ! ects of combined environmental stresses

is the psychophysical model. Stevens (1975) suggests thatthe sensation magnitude of a stimulus increases asa power function of the physical stimulus magnitude. Theexponent of the power function depends upon the par-ticular environmental stress. Knowing the exponent foreach stress the relative sensation produced for each canbe de " ned and physical levels of stimuli that produceequivalent sensations can be derived. This theoreticalmethod, which does not take account of individual di ! er-ences, is di $ cult to apply to practical situations.

There have been a number of experimental studies of combined stresses. These include the e ! ects of combinednoise and vibration on a cognitive task (Champion, 1981)and on tracking performance (Harris and Shoenberger,1980), and an experiment to determine levels of noise andvibration which produce equivalent sensations (Flemingand Gri $ n, 1975). Grether et al. (1971) investigated thee! ects of heat, noise, and vibration on a number of tasksand Bowman and Beckh (1979) investigated the com-bined e ! ects of acceleration, bu ! eting noise, temperature,and lighting levels on pilot performance in aircraft. Thepractical conclusion from these studies is that no generalguidelines can be provided. Methods of combining

the e!

ects of stresses have been proposed, which varyfrom &synergistic ' methods to considering the &most-severe component ' as being the best estimate of the com-bined e ! ect. A method that can be used to assessthe combined e ! ects of total environments is to obtainsubjective ratings of environments and use multiple re-gression techniques to provide a model that combinesenvironmental components. This has been used, forexample, to predict the satisfaction of aircraft passengers(Jacobson, 1980). However, although the regressionequation may be useful in the context within which it wasderived, it provides little understanding of the mecha-

nisms by which combined stresses a ! ect human occu-pants and should therefore not be used outside of thiscontext.

6. Discussion and conclusions

It is clear from the above discussions that there hasbeen a great deal of work on the e ! ects of light, noise,vibration, and thermal environments on the health, com-fort, and working e $ ciency of the occupants of buildings.Models exist which can provide realistic predictions of the e ! ects or probable e ! ects of components of environ-ments. In addition, general guidance on interactive e ! ectsand the e ! ects of total environments can be provided.The e ! ects of &total ' environments include ` 2 the sum of the physiological, psychological and social sensationsexperienced by people in or around buildings whichfollow from their use of the buildings a (Manning, 1968).Models of these &integrated e ! ects ' are not available andbuildings should also still be evaluated using subjective(and also possibly objective) methods.

It can be concluded that the ambitious objectives of

environmental ergonomics can now partially beachieved. More fundamental knowledge is still requiredon environmental interactions however. Future develop-ments in this area should lead to greater predictive powerof these models. The development of computer softwarewill allow the models to become readily available tothose who wish to design and evaluate buildings.Measurements or predictions of environmental para-meters will be used as inputs to computer programs of the models and the output will provide an indication of environmental e ! ects. However, the apparent sophistica-tion of the models and the ease and directness with whichassessmentscan be made may not necessarily indicate theaccuracy of any predictions. Further investigation of &total ' environments will still be required. The role of future computer aided design software in overall systemsdesign and evaluation will only be established by practi-cal experience.

Appendix A. International Standardization * Ergonomics of the Physical Environment

The following describes the current standards and activ-ity concerned with ergonomics of the physical environ-ment (for more detail the reader is referred to a SpecialIssue of Applied Ergonomics, Vol. 26, No. 4, August 1995).

International Standards in Ergonomics have been de-veloped since 1974 when ISO TC 159 was established atthe request of the International Ergonomics Association(IEA). Sub-committee ISO TC 159 SC5 &Ergonomics of the Physical Environment ' was established at the sametime and is responsible for over 30 work items which arerequests, by international voting, to produce a standard.The sub-committee has three working groups that devel-

op the standards. These are concerned with thermalenvironments, lighting and danger signals and commun-ication in noisy environments. Standards are produced



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according to established rules that involve single repres-entation of each member country. ISO has over 120member countries and those involved with SC5 areBelgium, Czech Republic, Denmark, Finland, France,Germany, Italy, Japan, Australia, Korea, Mexico, Neth-erlands, Poland, Slovakia, Sweden, Thailand, UK, USA.Some countries are more active than others, with sometaking an observer role. There is a democratic system of voting on draft standards through to " nal acceptanceor otherwise. People who produce the standardsare representatives from national bodies (BSIfor UK, ANSI for USA, etc.), appointed chairs andconvenors or co-opted experts. User involvement instandardisation therefore requires involvement in thatprocess.

A.1. Users of standards

The users of a standard are not easily de"

ned. Stan-dards are used for many reasons and by a number of people. In the context of the ergonomics of the physicalenvironment, users could be o $ ce workers who experi-ence the environments, building services engineers whodesign and monitor the environments, manufacturers of equipment, ergonomists who design jobs, health andsafety o $ cers who assess environments, other standardsmakers and more. A discussion of who the users of a standard will be and what will be the scope of thestandard, is the usual starting point in standard develop-ment. How to make it useable, however, is not, and theformal structure of standards does not encourage theproduction of useable standards. Standards for the ergo-nomics of the physical environment are generally pro-duced by experts in their " eld and are often consideredlimited in their usability. It is recognised that this must beaddressed.

Users are presently involved in standardisationthrough national bodies mainly by commenting on pro-posed standards. More active consumer groups will haverepresentation on national and international committees.Most standards concerned with the ergonomics of the

physical environment are developed by subject experts.In some cases, manufacturers and consumer groups havebeen involved, in particular in European standardization(EN standards can become ISO standards and vice versa,via the Vienna agreement). A standard concerned withskin burns caused by contact with hot surfaces has hadrepresentation from consumer groups, concerned thattemperatures for burn may be set too high and manufac-turers of cookers and chain saws concerned that they willincrease costs of production if they are too low. A stan-dard for working practices for cold environments hadtrade union representation and so on. Representation of

user groups will provide an important perspective butwill not necessarily create useable standards. Usability isthe domain of the ergonomist and would have to be

explicitly considered in the standardisation process.ISO rules and usability testing must become part of that process. The question &is the standards useable? 'could be added to a voting form with a positive voterequired.

A.2. ISO TC 159 SC5 * Ergonomics of the physical environment : summary of work

ISO TC159 SC5 produces international standards inthe ergonomics of the physical environment. As this hasa wide scope and standards are produced in other areas(e.g. vibration) within ergonomics TC 159 SC5 has beencon " ned to thermal environments (WG1), lighting(WG2) and danger signals and communication in noisyenvironments (WG3). Working Group 1 produces stan-dards concerned with heat stress, cold stress and thermalcomfort as well as supporting standards concerned with

the thermal properties of clothing and metabolic heatproduction due to activity. It also considers physiologicalmeasures, skin reaction to contact with hot, moderateand cold surfaces and thermal comfort requirements forpeople with special requirements. Working Group 2 isconcerned with the ergonomics of lighting and is stronglyguided by the international lighting commission (CIE).Working Group 3 considers communication in noisyenvironments including warning and danger signalsand speech. Recent new work items have included thee! ects of combined stress environments and also theperformance of glazing in terms of visual and thermalcomfort.

A.3. Published standards and standards in de velopment

ISO 7243: 1995 Hot environments * estimation of theheat stress on working man, based on the WBGT-index (wet bulb globe temperature).

ISO 7726: 1998, Thermal environments * instrumentsand methods for measuring physical quantities.

ISO 7730: 1994, Moderate thermal environments* determination of the PMV and PPD indices and

speci"

cation of the conditions for thermal comfort. ISO 7731: 1986, Danger signals for workplaces * au-ditory danger signals.

ISO 7933: 1989, Hot environments * analytical deter-mination and interpretation of thermal stress usingcalculation of required sweat rate.

ISO 8995: 1989, Principles of visual ergonomics * thelighting of indoor work systems.

ISO 8996: 1990, Ergonomics * determination of metabolic heat production.

ISO 9886: 1992, Evaluation of thermal strain byphysiological measurements.

ISO 9920: 1995, Ergonomics of the thermal environ-ment * estimation of the thermal insulation and evap-orative resistance of a clothing ensemble.



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ISO 9921-1: 1996, Ergonomic assessment of speechcommunication. Part 1: Speech interference level andcommunication distances for persons with normalhearing capacity in direct communication (SILmethod).

ISO 10551: 1995, Ergonomics of the thermal environ-ment * assessment of the in # uence of the thermalenvironment using subjective judgement scales.

ISO 11399: 1995, Ergonomics of the thermal environ-ment * principles and application of internationalstandards.

ISO 11428: 1994, Ergonomics * visual danger signals* general requirements, design and testing.

ISO 11429: 1994, Ergonomics * system of danger andnon-danger signals with sound and light.

A.3.1. Technical reports

ISO TR 11079 (Technical Report): 1993, Evaluation of cold environments * determination of required cloth-ing insulation, IREQ.

A.4. Current work programme ~ ISO TC 159 SC5

ISO 15742 Ergonomics of the Physical Environment* combined e ! ects of thermal environment, air pollu-tion, acoustics and illumination.

A.4.1. Ergonomics of the thermal en vironment * ISO TC 159 SC5 WG1

Revision of ISO 7933: 1989, Hot environments * ana-lytical determination and interpretation of thermalstress using calculation of required sweat rate.

Revision of ISO 8996: 1990, Ergonomics * determina-tion of metabolic heat production.

Revision of ISO 9886: 1992, Evaluation of thermalstrain by physiological measurements.

Revision of ISO 7730: 1993, Moderate thermal envi-ronments * determination of the PMV and PPD

indices and speci"

cation of the conditions for thermalcomfort. Revision of ISO TR 11079 (Technical Report): 1993 toan International Standard. Evaluation of cold envi-ronments * determination of required clothing insu-lation, IREQ.

ISO DIS 11371 Ergonomics of the thermal environ-ment * vocabulary and symbols.

ISO DIS 12894: 1993, Ergonomics of the thermalenvironment * medical supervision of individuals ex-posed to hot or cold environments.

ISO/ NP 13732 Part 1. Ergonomics of the thermal

environment * methods for the assessment of humanresponses to contact with surfaces. Part 1: Hot surfa-ces.

ISO CD 13732 Part 2. Ergonomics of the thermalenvironment * methods for the assessment of humanresponses to contact with surfaces. Part 2: Moderatesurfaces.

ISO/NP 13732 Part 3. Ergonomics of the thermalenvironment * methods for the assessment of humanresponses to contact with surfaces. Part 3: Cold surfa-ces.

ISO NP 14405: Ergonomics of the thermal environ-ment * evaluation of the thermal environment invehicles.

ISO NP 14415: Ergonomics of the thermal environ-ment * application of international standards to thedisabled, the aged and other handicapped persons.

ISO NP 15265: Ergonomics of the thermal environ-ment * risk of stress or discomfort.

ISO NP 15743: Ergonomics of the thermal environ-ment * working practices for cold indoor environ-

ments.

A.4.2. Lighting * ISO TC 159 SC5 WG2

Revision of ISO 8995, 1989: Principles of Visual ergo-nomics * the lighting of indoor work systems.

A.4.3. Danger signals and communication in noisy en vi-ronments * ISO TC 159 SC5 WG3

ISO 9921: Ergonomic assessment of speech commun-ication in noisy environments * revision of Part 1 andto include Parts 0, 2 and 3. Principles, criteria, predic-tion and assessment.

Revision of ISO 7731: 1986, Danger signals for work-places * auditory danger signals.

References

ACGIH, 1998. TLVs and BEIs: threshold limit values for chemicalsubstances and physical agents biological exposure indices. Ameri-can Conference of Government Industrial Hygienists, Cincinnati,USA.

American Society of Heating, Refrigerating and Air Conditioning En-gineers, 1966. Thermal Comfort Conditions, ASHRAE Standard55-66, New York.

BS 6472, 1984. Evaluation of human exposure to vibration in buildings(1 Hz to 80 Hz), British Standards Institution.

Bonney, R.A., 1995. Human responses to vibration. Principles andmethods. In: Wilson, J.R., Corlett, E.N. (Eds.), Evaluationof HumanWork. Taylor & Francis, London, ISBN 07484 0084-2.

Bowman, J.S., Beckh, J. von, 1979. Physiologic and performancemeasurements in simulated airborne combined stress environments.Aviat. Space Environ. Med. 50 (6), 604 } 608.

Boyce, P.R., 1981. Human Factors in Lighting. Applied Science Pub-lishers, London.

Broadbent, D.E., 1971. Decision and Stress. Academic Press, London.Burns, W., Robinson, A.W., 1970. Hearing and Noise in Industry.

HMSO, London.



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Burton, A.C., Edholm, Otto, G., 1955. Man in a Cold Environment.Edward Arnold, London.

Champion, A., 1981. E ! ects of noise and vibration on cognitive perfor-mance. M.Sc. Thesis, Loughborough University of Technology,UK.

CIBSE, 1994. Code for Interior Lighting. Chartered Institute of Build-ing Services Engineers, London.

CIE, 1978. Light as a true visual quantity: principles of measurement.

CIE Publication 41, 1978.Fanger, P.O., 1970. Thermal Comfort. Danish Technical Press, Copen-

hagen.Fields, J.M., Walker, J.G., 1980. Reactions to railway noise: a sur-

vey near railway lines in Great Britain. ISVR Technical ReportNo. 102.

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