7. Air Monitoring - osha.gov

1 7-17. Air MonitoringContentsIntroduction7-1 Measuring Instruments7-1 Direct-Reading Instruments7-2 Laboratory Analysis7-7 Site Monitoring7-7 Monitoring for IDLH and Other Dangerous Conditions7-8 General Onsite Monitoring7-9 Perimeter Monitoring7-9 Periodic Monitoring7-9 Personal Monitoring7-9 Variables of Hazardous Waste Site Exposure7-10 References7-11 IntroductionAirborne contaminants can present a significant threat to worker health and safety. Thus, identificationand quantification of these contaminants through air Monitoring is an essential component of a health andsafety program at a hazardous waste site. Reliable measurements of airborne contaminants are usefulfor: Selecting personal protective equipment. Delineating areas where protection is needed. Assessing the potential health effects of exposure Determining the need for specific medical Monitoring .

2 This chapter delineates the factors toconsider when conducting air Monitoring at a hazardous waste site. It presents strategies forassessing airborne contamination at hazardous waste sites and describes instruments andmethods for measuring InstrumentsThe purpose of air Monitoring is to identify and quantify airborne contaminants in order to determine thelevel of worker protection needed. Initial screening for identification is often qualitative, , thecontaminant, or the class to which it belongs, is demonstrated to be present but the determination of itsconcentration (quantification) must await subsequent testing. Two principal approaches are available foridentifying and/or quantifying airborne contaminants: The onsite use of direct-reading instruments. Laboratory analysis of air samples obtained by gas sampling beg, filter, sorbent, or wet-contaminant collection InstrumentsDirect-reading instruments were developed as early warning devices for use in industrial settings, wherea leak or an accident could release a high concentration of a known chemical into the ambientatmosphere.

3 Today, some direct-reading instruments can detect contaminants in concentrations down toone part contaminant per million parts of air (ppm), although quantitative data are difficult to obtain whenmultiple contaminants are present. Unlike air sampling devices, which are used to collect samples forsubsequent analysis in a laboratory, direct reading instruments provide information at the time ofsampling, enabling rapid instruments may be used to rapidly detect flammable or explosive atmospheres, oxygendeficiency, certain gases and vapors, and ionizing radiation. They are the primary tools of initial sitecharacterization. The information provided by direct-reading instruments can be used to instituteappropriate protective measures ( , personal protective equipment, evacuation), to determine the mostappropriate equipment for further Monitoring , and to develop optimum sampling and analytical direct-reading instruments have inherent constraints in their ability to detect hazards: They usually detect and/or measure only specific classes of chemicals.

4 Generally, they are not designed to measure and/or detect airborne concentrations below 1 ppm. Many of the direct-reading instruments that have been designed to detect one particularsubstance also detect other substances (interference) and, consequently, may give is imperative that direct-reading instruments be operated, and their data interpreted, by qualifiedindividuals who are thoroughly familiar with the particular device's operating principles and limitations andwho have obtained the device's latest operating instructions and calibration curves. At hazardous wastesites, where unknown and multiple contaminants are the rule rather than the exception, instrumentreadings should be interpreted conservatively. The following guidelines may facilitate accurate recordingand interpretation: Calibrate instruments according to the manufacturer's instructions before and after every use.

5 Develop chemical response curves if these are not provided by the instrument manufacturer. Remember that the instrument's readings have limited value where contaminants are recording readings of unknown contaminants, report them as "needle deflection" or"positive instrument response" rather than specific concentrations ( , ppm). Conduct additionalmonitoring at any location where a positive response occurs. A reading of zero should be reported as "no instrument response" rather than "clean" becausequantities of chemicals may be present that are not detectable by the instrument. The survey should be repeated with several detection systems to maximize the number ofchemicals 7-1 and 7-2 list several direct-reading instruments and the conditions and/or substances theymeasure. The flame ionization detector (FID) and the photoionization detector (PID) (see Table 7-1) arecommonly used at hazardous waste sites.

6 However, some of these devices may not detect someparticularly toxic agents, including hydrogen cyanide and hydrogen sulfide. Thus, these devices must besupplemented with other methods of 7-1. Some Direct-Reading Instruments for General SurveyINSTRUMENTHAZARDMONITOREDAPPLICATI ONDETECTIONMETHODLIMITATIONSEASE OFOPERATIONGENERAL CAREANDMAINTENANCETYPICALOPERATINGTIMESC ombustible GasIndicator (CGI)Combustiblegases theconcentration of acombustible gasor filament, usuallymade of platinum,is heated byburning thecombustible gasor vapor. Theincrease in heat depends, inpart, on the differencebetween the calibrationand is a functionof the differences inthe chemical andphysical propertiesbetween the calibrationgas and the gas filament can bedamaged by certaincom-pounds such assilicones, halides,tetraethyl lead, not provide avalid reading userequires thatoperator understandthe operatingprinciples orreplace immedi-ately before be usedfor as long asthe batterylasts, or for therecommendedintervalbetweencalibration s,whichever IonizationDetector (FID)with GasChromatographyOptionMany organicgases survey mode,detects the totalconcentration ofmany organicgases and gas chroma-tography (GC)mode, identifiesand and vaporsare ionized in aflame.

7 A currentis produced inproportion to thenumber of carbonatoms not detectinorganic gases andvapors, or somesynthetics. Sensitivitydepends on not be used attemperatures less than40oF (4oC).Difficult to absolutelyRequires experienceto interpret datacorrectly, especiallyin the GC identifica-tion requires cali-bration with thespecific analyte orreplace fuel and/orcombustion airsupply routinemaintenance asdescribed in hours; 3hours with stripchart OFOPERATIONGENERAL CAREANDMAINTENANCETYPICALOPERATINGTIMESI n survey mode,all the organiccom-pounds areionized anddetected at thesame time. In GCmode, volatilespecies are concentrations ofcontaminants ofoxygen-deficientatmospheres requiresystem survey mode,readings can be onlyreported relative to thecalibration for SurveyInstrumentGammaradiationEnvironmen talradiation not measurealpha or beta easy tooperate, but requiresexperience tointerpret , good infield be calibratedannually at aspecialized facilityCan be usedfor as long asthe batterylasts, or for therecommendedintervalbetweencalibration swhichever Infrared(IR) Spectro-photometerMany gasesand ofmany gases andvapors in toquantify one- differentfrequencies of IRthrough thesample.

8 The fre-quenciesadsorbed andspecific for the field, must makerepeated passes toachieve 115-volt approved for usein a potentiallyflammable or by watervapor and carbonRequires personnelwith extensiveexperience in specified OFOPERATIONGENERAL vapors andhigh moisture mayattach the instrumentsoptics, which mustthen be (UV)PhotoionizationDetector (PID)Many organicand someinorganicgases totalconcentrations ofmany organic andsome inor-ganicgases and identi-fication ofcompounds ispossible if morethan one probe moleculesusing UVradiation;produces acurrent that ispropor-tional tothe number not not detect acompound if the probeused has a lowerenergy level than thecompound s may changewhen gases are voltage sourcesmay interfere can only bereported relative to thecalibration is affectedby high userequires that theoperator understandthe operating prin-ciples and proced-ures, and be compe-tent in calibrating,reading, andinterpreting orreplace cleanlamp cleanand maintain theinstrument hours; 5hours with stripchart 7-2.

9 Some Direct-Reading Instruments for Specific SurveyINSTRUMENTHAZARDMONITOREDAPPLICATI ONDETECTIONMETHODLIMITATIONSEASE OFOPERATIONGENERAL CAREANDMAINTENANCETYPICALOPERATINGTIMESD irect-ReadingColorimetricIndicator TubesSpecificgases ofspecific gases compoundreacts with theindicator chemicalin the tube,producing a stainwhose length orcolor change isproportional to thecompound measuredconcentration of thesame compound mayvary among differentmanu-facturers similar chemi-cals sources oferror are (1) how theoperator judges stain send-point, and (2) thetube s by operatortraining andexpertise not use apreviously openedtube even if theindicator chemical isnot MeterOxygen (O2)Measures thepercentage of O2in anelectrochemicalsensor to measurethe partialpressure of O2 inthe air and con-verts that readingto O2 be calibratedprior to use to com-pensate for altitudeand gases,especially oxidantssuch as ozone, canaffect dioxide (CO2)poisons the userequires that theoperatorunderstand theoperating principlesand detectorcell according tomanufacturer or replacebatteries prior toexpiration of thespecified the ambient air ismore than , replace the O2detector to 12 AnalysisDirect-reading personal monitors are available for only a few specific substances and are rarelysensitive enough to measure the minute ( , parts of contaminant per billion parts of air)quantities of contaminants which may, nevertheless induce health changes.

10 Thus to detectrelatively low-level concentrations of contaminants, long-term or "full-shift" personal air samplesmust be analyzed in a laboratory. Full-shift air samples for some chemicals may be collected withpassive dosimeters, or by means of a pump which draws air through a filter or sorbent. Table 7-3lists some sampling and analytical techniques used at hazardous waste of the appropriate sampling media largely depends on the physical state of thecontaminants. For example, chemicals such as PCBs (polychlorinated biphenyls) and PNAs(polynuclear aromatic hydrocarbons) occur as both vapors and particulate-bound dual-media system is needed to measure both forms of these substances. The volatilecomponent is collected on a solid adsorbent and the nonvolatile component is collected on afilter. More than two dozen dual-media sampling techniques have been evaluated by NIOSH [l,2].