OVERVIEW OF INDUSTRIAL OVERVIEW OF INDUSTRIAL HYGIENEHYGIENE

PRINCIPLES OF PRINCIPLES OF EVALUATING WORKER EVALUATING WORKER

EXPOSUREEXPOSURE

DEFINITIONDEFINITION

Industrial Hygiene (IH) is that science Industrial Hygiene (IH) is that science devoted to the anticipation, recognition, devoted to the anticipation, recognition, measurement, evaluation, and control of measurement, evaluation, and control of adverse occupational stresses or agents adverse occupational stresses or agents which could cause sickness and impaired which could cause sickness and impaired health among workers and the health among workers and the community. The basic goal of IH (i.e. community. The basic goal of IH (i.e. occupational hygiene) is to promote a occupational hygiene) is to promote a safe and healthful work environment.safe and healthful work environment.

OCCUPATIONAL HYGIENEOCCUPATIONAL HYGIENE

The science and art of anticipating, The science and art of anticipating, recognizing, evaluating, and controlling recognizing, evaluating, and controlling health hazards in the workplace. The health hazards in the workplace. The purpose of this introduction is to provide an purpose of this introduction is to provide an understanding of the general principles of understanding of the general principles of evaluating worker exposures in the industrial evaluating worker exposures in the industrial environment. environment.

IH FOCUSIH FOCUS

1.1. Hazardous agents in workplaceHazardous agents in workplace

2.2. Health effects associated withHealth effects associated with

excessive exposuresexcessive exposures

3.3. Occupational Exposure Limits Occupational Exposure Limits (OELs)(OELs)

for each agentfor each agent

4.4. Workforce organization and staffingWorkforce organization and staffing

5.5. Significant sources of exposure; tasks Significant sources of exposure; tasks and work procedures involvedand work procedures involved

6.6. Control measuresControl measures

IH ELEMENTSIH ELEMENTS

AnticipationAnticipation RecognitionRecognition EvaluationEvaluation ControlControl

ANTICIPATIONANTICIPATION

Expectation of potential health hazards is Expectation of potential health hazards is generally more difficult for the entry-level, generally more difficult for the entry-level, inexperienced occupational hygienist since skills in inexperienced occupational hygienist since skills in anticipation generally increase with experience. anticipation generally increase with experience. Ability to recognize potential health hazards as Ability to recognize potential health hazards as well as knowledge of scientific developments, new well as knowledge of scientific developments, new technologies, and regulatory requirements, etc.technologies, and regulatory requirements, etc.

RECOGNITIONRECOGNITION

Requires knowledge and understanding of Requires knowledge and understanding of workplace environmental stresses and effects on workplace environmental stresses and effects on health of the worker related to processes and health of the worker related to processes and control measures; inventory of chemical, control measures; inventory of chemical, biological, and physical hazards; potential biological, and physical hazards; potential chemical hazards are determined by toxicity and chemical hazards are determined by toxicity and also conditions of use. Involves collection of also conditions of use. Involves collection of available information along with the application of available information along with the application of IH principles. IH principles.

RECOGNITIONRECOGNITION

Detailed information to be obtained Detailed information to be obtained regarding types of hazardous materials regarding types of hazardous materials used, type of job operation, worker used, type of job operation, worker exposures and patterns, levels of air exposures and patterns, levels of air contaminants, exposure duration, control contaminants, exposure duration, control measures, etc. Consult product information. measures, etc. Consult product information. Develop workplace characterization which Develop workplace characterization which results in defining “exposure groups” for results in defining “exposure groups” for same tasks/similar manner. same tasks/similar manner.

TOXICITY VS. HAZARDTOXICITY VS. HAZARD

ToxicityToxicity is the capacity of a material to is the capacity of a material to produce injury or harm to living tissue produce injury or harm to living tissue when the chemical has reached a when the chemical has reached a sufficient concentration at a certain site sufficient concentration at a certain site in the human body. in the human body.

HazardHazard is the probability that this is the probability that this concentration will occur within the body; concentration will occur within the body; affected by many factor/elements affected by many factor/elements generally related to conditions of use. generally related to conditions of use.

EVALUATIONEVALUATIONInvolves observation as well as monitoring Involves observation as well as monitoring and and use of analytical methodsuse of analytical methods required to required to detect the extent of exposuredetect the extent of exposure; decision-; decision-making process resulting in an making process resulting in an opinionopinion on the on the degree of health hazards and/or stressors that degree of health hazards and/or stressors that exist; determine significance (e.g. exist; determine significance (e.g. subjective/objective judgment); extent of subjective/objective judgment); extent of potential health hazards based on potential health hazards based on comparisons of environmental measurements comparisons of environmental measurements with current governmental regulations and with current governmental regulations and recommended technical guidelines.recommended technical guidelines.

EFFECTIVE EVALUATIONEFFECTIVE EVALUATION

Utilize a Utilize a multi-disciplinary approachmulti-disciplinary approach including including knowledge-based technical information. knowledge-based technical information. ContributionsContributions include: include: occupational hygieneoccupational hygiene, , chemistrychemistry, , engineeringengineering, , health physicshealth physics, medicine, , medicine, epidemiology, epidemiology, toxicologytoxicology, and nursing disciplines , and nursing disciplines as well as management and manufacturing as well as management and manufacturing expertise.expertise.

Integrate knowledgeIntegrate knowledge and develop and develop control control strategies for potential risk limitationstrategies for potential risk limitation..

Consider team-based efforts of personnel.Consider team-based efforts of personnel.

EVALUATIONEVALUATION

Exposure assessment: initial qualitative method Exposure assessment: initial qualitative method for prioritization; then, semi-quantitative (i.e. for prioritization; then, semi-quantitative (i.e. mathematical modeling) or quantitative (i.e. mathematical modeling) or quantitative (i.e. monitoring) methodologies.monitoring) methodologies.

Air monitoring can be involved for quantitative Air monitoring can be involved for quantitative assessment; breathing zone exposures preferred.assessment; breathing zone exposures preferred.

On-going process: feedback from multiple On-going process: feedback from multiple sources of information; refine exposure estimates; sources of information; refine exposure estimates; evaluate control effectiveness; priorities change!evaluate control effectiveness; priorities change!

EXPOSURE ASSESSMENTEXPOSURE ASSESSMENT

Control exposures Control exposures Compliance determinations Compliance determinations Program management (i.e. respiratory; Program management (i.e. respiratory;

hearing/noise; medical surveillance, etc.)hearing/noise; medical surveillance, etc.) Epidemiologic studiesEpidemiologic studies Health complaint investigationsHealth complaint investigations Risk assessmentRisk assessment Proposed change evaluations to processProposed change evaluations to process

CONTROLCONTROL

Involves the reduction of environmental Involves the reduction of environmental stresses to levels that the worker can stresses to levels that the worker can tolerate without impairment of health or tolerate without impairment of health or productivity; various general control productivity; various general control methods employed for accomplishments in methods employed for accomplishments in an efficient and effective manner.an efficient and effective manner.

CONTROLCONTROL

Defined as the adjustment or regulation of Defined as the adjustment or regulation of an operation to meet a standard or an operation to meet a standard or guideline, the reduction or prevention of guideline, the reduction or prevention of contaminant release, and the ability to contaminant release, and the ability to contain a stressor/hazard. contain a stressor/hazard.

CONTROL METHODSCONTROL METHODS

EngineeringEngineering – remove the hazard; should be – remove the hazard; should be primarily considered.primarily considered.

AdministrativeAdministrative – reduce exposures through – reduce exposures through scheduling/job rotation; housekeeping; scheduling/job rotation; housekeeping; employee training; not generally favored.employee training; not generally favored.

Personal Protective EquipmentPersonal Protective Equipment (PPE) – use (PPE) – use should be secondary to design and should be secondary to design and implementation of engineering controls.implementation of engineering controls.

ENGINEERING CONTROLSENGINEERING CONTROLS

• SubstitutionSubstitution

• Change in processChange in process

• Source modificationSource modification

• IsolationIsolation

• EnclosureEnclosure

• Wet methodsWet methods

• VentilationVentilation

ADMINISTRATIVE CONTROLSADMINISTRATIVE CONTROLS

EXAMPLESEXAMPLES::

-- Arranging work schedules and the Arranging work schedules and the related frequence/duration to limit related frequence/duration to limit employee exposures to health hazards.employee exposures to health hazards.

-- Transferring employees at PELs to an Transferring employees at PELs to an environment where additional environment where additional

exposure exposure is not anticipated.is not anticipated.

-- Housekeeping; preventive Housekeeping; preventive maintenance.maintenance.

ADMINISTRATIVE CONTROLSADMINISTRATIVE CONTROLS

Administrative controls must be designed Administrative controls must be designed only by knowledgeable health and safety only by knowledgeable health and safety professionals, and used cautiously. professionals, and used cautiously.

Not as satisfactory as engineering controls Not as satisfactory as engineering controls and have been criticized as a means of and have been criticized as a means of spreading exposures instead of reducing or spreading exposures instead of reducing or eliminating personal exposures.eliminating personal exposures.

PPEPPE

PPE may be used to protect the worker PPE may be used to protect the worker when it is not feasible to render the working when it is not feasible to render the working environment completely safe. Examples: environment completely safe. Examples: eye/foot/head protection, gloves, respirators. eye/foot/head protection, gloves, respirators.

Considered a secondary control method to Considered a secondary control method to engineering and administrative controls and engineering and administrative controls and should be used as a last resort.should be used as a last resort.

EFFECTIVE IH PROGRAMEFFECTIVE IH PROGRAM

Applies knowledge to the anticipation and Applies knowledge to the anticipation and recognition of health hazards arising out of recognition of health hazards arising out of work operations and processes, evaluation work operations and processes, evaluation and measurement of the magnitude of the and measurement of the magnitude of the hazard based on past experience and hazard based on past experience and study, and control of the occupational study, and control of the occupational hazards.hazards.

POTENTIAL HAZARDSPOTENTIAL HAZARDS

ChemicalChemical PhysicalPhysical BiologicalBiological ErgonomicErgonomic

CHEMICAL HAZARDSCHEMICAL HAZARDS

HydrocarbonsHydrocarbons SolventsSolvents Oil MistOil Mist Dust (Total and Respirable)Dust (Total and Respirable) Crystalline SilicaCrystalline Silica FormaldehydeFormaldehyde Carbon MonoxideCarbon Monoxide Airborne FibersAirborne Fibers

PHYSICAL HAZARDSPHYSICAL HAZARDS

NoiseNoise RadiationRadiation

-- IonizingIonizing-- Non-ionizingNon-ionizing

LightingLighting Heat/Cold StressHeat/Cold Stress Pressure Extremes Pressure Extremes

BIOLOGICAL HAZARDSBIOLOGICAL HAZARDS

BioaerosolsBioaerosols Surface/Bulk ContaminationSurface/Bulk Contamination TuberculosisTuberculosis Bloodborne PathogensBloodborne Pathogens Indoor Air Quality IssuesIndoor Air Quality Issues

ERGONOMIC HAZARDSERGONOMIC HAZARDS

Musculoskeletal DisordersMusculoskeletal Disorders Cumulative Trauma DisordersCumulative Trauma Disorders Carpal Tunnel SyndromeCarpal Tunnel Syndrome Material Handling/LiftingMaterial Handling/Lifting Workplace Design ConsiderationsWorkplace Design Considerations

OTHER HAZARDSOTHER HAZARDS

Confined SpacesConfined Spaces Waste ManagementWaste Management Lab Health and SafetyLab Health and Safety Emergency PlanningEmergency Planning Etc. . . Etc. . .

EXPOSURE ASSESSMENTEXPOSURE ASSESSMENT

Determination or estimation of the Determination or estimation of the magnitudmagnitude, e, frequencyfrequency, , durationduration, and , and route of exposureroute of exposure..

Determine purpose and scope of survey Determine purpose and scope of survey Become familiar with process operationsBecome familiar with process operations Perform the preliminary, qualitative surveyPerform the preliminary, qualitative survey Conduct workplace monitoring as a Conduct workplace monitoring as a

quantitative evaluationquantitative evaluation Interpret the sampling results.Interpret the sampling results.

TYPES OF EVALUATIONSTYPES OF EVALUATIONS Comprehensive exposure assessment to Comprehensive exposure assessment to

identify and quantify health hazards identify and quantify health hazards Assess compliance with regulatory Assess compliance with regulatory

standards and/or technical guidelinesstandards and/or technical guidelines Review exposures based on complaints +Review exposures based on complaints + Exposure assessment for medical and Exposure assessment for medical and

epidemiological studies +epidemiological studies + Determine effectiveness of engineering Determine effectiveness of engineering

and/or administrative controls +and/or administrative controls +

COMPREHENSIVE EXPOSURE COMPREHENSIVE EXPOSURE ASSESSMENTASSESSMENT

Primary objective is to determine the Primary objective is to determine the acceptability of exposures to health hazards acceptability of exposures to health hazards for all workers in designated work areas or for all workers in designated work areas or for specific operations. for specific operations.

Based on identification and Based on identification and quantification/estimation of exposures to quantification/estimation of exposures to workplace stressors, then use of walk-through workplace stressors, then use of walk-through survey procedures for hazard identification, survey procedures for hazard identification, and subsequently, evaluation techniques to and subsequently, evaluation techniques to estimate employee exposure levels are estimate employee exposure levels are employed. employed.

COMPLIANCE SURVEYCOMPLIANCE SURVEY

Exposure to stressors are quantified and Exposure to stressors are quantified and evaluated by comparison to published health evaluated by comparison to published health standards, Permissible Exposure Limits standards, Permissible Exposure Limits (PELs) or technical recommended guidelines (PELs) or technical recommended guidelines such as American Conference of such as American Conference of Governmental Industrial Hygienists (ACGIH) Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs). Threshold Limit Values (TLVs).

Determine compliance vs. non-compliance. Determine compliance vs. non-compliance.

PROCESS OPERATIONSPROCESS OPERATIONS Physical facility layout Physical facility layout Process description and stepsProcess description and steps Inventory of process stressors/hazards Inventory of process stressors/hazards Worker job classificationsWorker job classifications Worker health statusWorker health status Control measures in place Control measures in place Results from past evaluationsResults from past evaluations Other associated process hazardsOther associated process hazards

PROCESS METHODOLOGYPROCESS METHODOLOGY

Information obtained through interviews, Information obtained through interviews, personal/visual observations, technical personal/visual observations, technical process information, and record reviews.process information, and record reviews.

A walk-through survey is an important A walk-through survey is an important methodology to understand, verify, and/or methodology to understand, verify, and/or modify documentation; look for potential modify documentation; look for potential sources of health hazards and chemical air sources of health hazards and chemical air contaminants and physical agents. contaminants and physical agents.

INVENTORYINVENTORY

Hazard/Stressor listing for identification Hazard/Stressor listing for identification Chemical and physical agentsChemical and physical agents Toxicological information; reference sourcesToxicological information; reference sources Occupational Exposure Limits (OELs)Occupational Exposure Limits (OELs)

e.g. OSHA PELs, ACGIH TLVs, e.g. OSHA PELs, ACGIH TLVs,

NIOSH RELs, AIHA WEELs, NIOSH RELs, AIHA WEELs,

ANSI, NIOSH Pocket GuideANSI, NIOSH Pocket Guide

JOB CLASSIFICATIONS/JOB CLASSIFICATIONS/WORK HEALTH STATUSWORK HEALTH STATUS

Formal job descriptions, and personnel Formal job descriptions, and personnel interviews with employees/supervisors.interviews with employees/supervisors.

Worker health status – medical surveillance Worker health status – medical surveillance for health hazard recognition and workplace for health hazard recognition and workplace logs of incidents/injuries/illnesses for logs of incidents/injuries/illnesses for assistance with stressor identification. assistance with stressor identification.

PAST EVALUATIONS/PAST EVALUATIONS/IDENTIFY POTENTIAL HAZARDSIDENTIFY POTENTIAL HAZARDS

Review of past occupational hygiene or Review of past occupational hygiene or related evaluations. Determine: time related evaluations. Determine: time elapsed; process changes, identification of elapsed; process changes, identification of significant problems, and/or other indicators.significant problems, and/or other indicators.

Personnel interviews and site review. Get Personnel interviews and site review. Get workers involved in the familiarization step workers involved in the familiarization step of a survey to assist with acceptance. of a survey to assist with acceptance.

PRELIMINARY ASSESSMENT - PRELIMINARY ASSESSMENT - QUALITATIVE QUALITATIVE

Familiarity with process/operation to Familiarity with process/operation to qualitatively evaluate magnitude of stressors qualitatively evaluate magnitude of stressors without benefit of instrumentation. without benefit of instrumentation.

Visual observations; use of senses (i.e. Visual observations; use of senses (i.e. smell); inspection of control measures smell); inspection of control measures implemented and effectiveness; and, PPE. implemented and effectiveness; and, PPE.

WORKPLACE MONITORING -WORKPLACE MONITORING -QUANTITATIVE EVALUATIONQUANTITATIVE EVALUATION

Document exposure levels either by Document exposure levels either by measurement or use of semi-quantitative measurement or use of semi-quantitative methods. Strategy developed depends on methods. Strategy developed depends on the reason for evaluation. Purpose is FIRST!the reason for evaluation. Purpose is FIRST!Sampling objectives: Sampling objectives: EITHEREITHER engineering engineering testing, surveillance, or control; testing, surveillance, or control; OROR compliance, health research, or compliance, health research, or epidemiological purposes.epidemiological purposes.

STRESSOR IDENTIFICATION/STRESSOR IDENTIFICATION/CONCENTRATION ESTIMATION CONCENTRATION ESTIMATION

Hazard information by familiarization and Hazard information by familiarization and then prioritization (probability/consequence then prioritization (probability/consequence of overexposure) based on significance for of overexposure) based on significance for monitoring. monitoring.

Probable range of contaminant Probable range of contaminant concentrations to assist with sampling concentrations to assist with sampling strategy development and facilitate selection strategy development and facilitate selection of monitoring methods and/or specific of monitoring methods and/or specific equipment for assessment. equipment for assessment.

SAMPLING AND ANALYTICALSAMPLING AND ANALYTICALMETHOD SELECTIONMETHOD SELECTION

Use of accurate, sensitive, specific, and Use of accurate, sensitive, specific, and reproducible analytical methods and proper reproducible analytical methods and proper calibrated sampling equipment. Knowledge of calibrated sampling equipment. Knowledge of interferences and detection limits.interferences and detection limits.Principles – validated methods (OSHA, Principles – validated methods (OSHA, NIOSH).NIOSH).Specificity, selectivity, and other Specificity, selectivity, and other considerations for direct-reading instruments.considerations for direct-reading instruments.Limitations - combine workplace observations Limitations - combine workplace observations with measurements for result interpretation.with measurements for result interpretation.

EQUIPMENT DECISIONSEQUIPMENT DECISIONS Type of analysis or information required Type of analysis or information required Efficiency of the instrumentEfficiency of the instrument Reliability of the instrument under various Reliability of the instrument under various

field use conditionsfield use conditions Exposure assessment for medical and Exposure assessment for medical and

epidemiological studies epidemiological studies Portability and ease of instrument use Portability and ease of instrument use Personal choice of IH based on past Personal choice of IH based on past

experience and other factors experience and other factors

EQUIPMENT SELECTIONEQUIPMENT SELECTION

Calibration – necessary to insure data Calibration – necessary to insure data representative of field exposures; results representative of field exposures; results based on accuracy of instruments (i.e. based on accuracy of instruments (i.e. direct-reading) and/or sampling and direct-reading) and/or sampling and analytical methods; pre- and post-calibration analytical methods; pre- and post-calibration to determine air sample volume; to determine air sample volume; temperature/pressure adjustmentstemperature/pressure adjustments

IH use of proper PPE during field IH use of proper PPE during field assessments assessments

SAMPLING STRATEGY SAMPLING STRATEGY

Overall plan or framework for sampling that Overall plan or framework for sampling that may include the type and number of may include the type and number of samples to be collected; the methods to be samples to be collected; the methods to be used, and their accuracy, and the objectives used, and their accuracy, and the objectives for monitoring. for monitoring.

Decision made with confidence and Decision made with confidence and minimum cost and effort. minimum cost and effort.

Complicated by numerous variables. Complicated by numerous variables.

SAMPLNG STRATEGYSAMPLNG STRATEGY

WHAT and WHY? WHAT and WHY? Where to sample?Where to sample? When to sample?When to sample? How long to sample?How long to sample? Whom to sample?Whom to sample? How many samples to collect?How many samples to collect? How should the samples be obtained?How should the samples be obtained?

WHERE???WHERE???

Personal or areaPersonal or area Breathing zoneBreathing zone Location(s) are dictated by NeedLocation(s) are dictated by Need Source of contaminants by AreaSource of contaminants by Area

WHEN???WHEN???

Determined by information required Determined by information required Type of operation assessedType of operation assessed Multiple shiftsMultiple shifts Geographic/climatologic conditions Geographic/climatologic conditions

HOW LONG???HOW LONG???

Minimum time is usually determined by the Minimum time is usually determined by the time interval necessary to obtain a sufficient time interval necessary to obtain a sufficient amount of the contaminant on the sample amount of the contaminant on the sample media for laboratory analysis. media for laboratory analysis.

Sensitivity of analytical procedureSensitivity of analytical procedure Dependent on contamination concentrationDependent on contamination concentration Full work shift for complianceFull work shift for compliance Work tasks; partial periods; multiple Work tasks; partial periods; multiple

samples to measure entire work shiftsamples to measure entire work shift

WHOM???WHOM???

Depends on purpose of monitoring. Depends on purpose of monitoring. For compliance, then sample maximum risk For compliance, then sample maximum risk

employees with highest exposures. employees with highest exposures. Random sample of employee by exposure Random sample of employee by exposure

group for a comprehensive assessmentgroup for a comprehensive assessment

HOW MANY???HOW MANY??? Dependent on the purpose of workplace Dependent on the purpose of workplace

monitoring. monitoring. For comprehensive assessment, a minimum For comprehensive assessment, a minimum

of six samples for each exposure group may of six samples for each exposure group may be needed for a decision of acceptability. be needed for a decision of acceptability.

With time and budget constraints, semi-With time and budget constraints, semi-quantitative methods may be used. No set quantitative methods may be used. No set rule! rule!

Use personal experience to collect optimal Use personal experience to collect optimal sample number given budgetary constraints. sample number given budgetary constraints.

HOW???HOW???

Instrument choice depends on:Instrument choice depends on:-- Portability and ease of usePortability and ease of use-- Efficiency and analytical methodEfficiency and analytical method-- Reliability under various conditions of Reliability under various conditions of field usefield use-- Type of analysis or information required Type of analysis or information required

The choice of instrumentation and testing The choice of instrumentation and testing and analytical procedures is ultimately and analytical procedures is ultimately dependent on the capabilities of the dependent on the capabilities of the analytical laboratory.analytical laboratory.

SAMPLE COLLECTIONSAMPLE COLLECTION

Follow strategy so as not to bias results or Follow strategy so as not to bias results or compromise the integrity of the conclusions. compromise the integrity of the conclusions.

Adjustments or modifications as needed Adjustments or modifications as needed Phased sampling strategy as an optionPhased sampling strategy as an option Understand procedures; equipment/supplies Understand procedures; equipment/supplies Understand impact on the work environment Understand impact on the work environment Recordkeeping – extensive notes and INFORecordkeeping – extensive notes and INFO Handling samples – labelingHandling samples – labeling

SAMPLING AND ANALYTICAL SAMPLING AND ANALYTICAL PROCEDURESPROCEDURES

Selection of measurement method depends Selection of measurement method depends on sampling strategy requirements and on sampling strategy requirements and purpose of workplace monitoring based on: purpose of workplace monitoring based on:

– duration of sampling [TWA vs. STEL], duration of sampling [TWA vs. STEL],

– sensitivity of the method/detection limit, sensitivity of the method/detection limit,

– freedom from interferences/result bias, freedom from interferences/result bias,

– time to reporting of results, time to reporting of results, – accuracy.accuracy.

INTERPRETATION OF INTERPRETATION OF SAMPLING RESULTSSAMPLING RESULTS

ConcentrationsConcentrations Calculations based on time periods Calculations based on time periods Test statisticsTest statistics Professional judgment – acute/chronicProfessional judgment – acute/chronic Information for data interpretationInformation for data interpretation

-- Precise nature of material/agentPrecise nature of material/agent

-- Intensity/magnitude of exposureIntensity/magnitude of exposure

-- Reliable knowledge of frequency/duration Reliable knowledge of frequency/duration

COMPARISONSCOMPARISONS

TWAs vs. STELSTWAs vs. STELS Best sampling strategy for full shift Best sampling strategy for full shift

integrated personal sampling; short-term integrated personal sampling; short-term tasks add more variability [peak/ceiling - tasks add more variability [peak/ceiling - instantaneous]; general area samples are instantaneous]; general area samples are not specifically recommended.not specifically recommended.

OELs – direct result comparison with OSHA OELs – direct result comparison with OSHA PELs, ACGIH TLVs, NIOSH RELs, AIHA PELs, ACGIH TLVs, NIOSH RELs, AIHA WEELs, etc.WEELs, etc.