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Air MonitoringInstructional Goal:

Enable participants to recognize the

value of direct-reading instruments inproviding immediate air concentrationresults at a hazardous waste site.

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Sampling Methods

Area sampling

involves placing collection devices within

designated areas and operating them overspecific periods of time.

Personal sampling involves collecting samples from within the

breathing zone of an individual, sometimesby the individual wearing a sampling device.

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Instantaneous Sample

are collected over brief periods of time

grab-type sample

examines stable contaminant

concentrations or peak levels of shortduration.

require highly sensitive analytical methodsdue to the small sample volume

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Air Monitoring Data is used to

assess health risks

determine location where PPE must be worn

and correct PPE to wear determine actual or potential effects on the

environment

select actions to mitigate the hazards determine the effectiveness of

decontamination activities

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Sampling System

sampling instrument or system chosendepends on a number of factors:

instrument or system efficiency

operational reliability

ease of use and portability

availability of the instrument andcomponent parts

information or analysis desired

calibration requirements

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Air Monitoring Instruments

must be

portable and rugged

easy to operate

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Air Monitoring Instruments

must be Inherently Safe

explosion-proof

intrinsically safe

purged

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Air Monitoring Instruments must

give Reliable and Useful Results

Response time

is the length of time the monitor takes fromwhen it "senses" a contaminant until itgenerates data. For direct-readinginstruments, response times may range

from a few seconds to several minutes.

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give Reliable and Useful ResultsSensitivity defined as the ability of an instrument to

accurately measure changes inconcentration. Sensitive instruments candetect small changes in concentration.

It is important to use an instrument with

an operating range that will measure theambient concentrations on-site.

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give Reliable and Useful ResultsSelectivity the ability of an instrument to detect and

measure a specific chemical or group ofsimilar chemicals.

Interferences from other chemicals canaffect the accuracy of the instrument

reading by producing a similar response.

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Accuracy the relationship between a true value (i.e.,

the actual concentration of a contaminant)

and the instrument reading.

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Precision

a statistical measurement ofan instrument's ability toreproduce a reading.

When an instrument does notreceive routine maintenancethe precision of the readingsmay change (become morerandom) this can affect theamount of error in the data

collected.

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BenchCalibration

follow manufacturers directions

for calibration to ensure accuratefield data

use standard sample of knownconcentration for calibration

adjust the instrument read-out sothat it corresponds to the actualconcentration

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Monitoring Equipment

Direct-Read Instruments

oxygen availability monitor

combustibility monitor

toxic atmosphere monitor

radiation monitor

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Oxygen Indicators

20.8% O2 isnormal air

at and below 19.5% O2 in air, O2 deficient

either displaced by another gas or consumed by combustion or reaction

> 23% O2 in air, increased risk of

combustion (possible oxidizer present)

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Combustible Gas Monitor

measures concentration of flammablevapor or gas in air

reads in % Lower Explosion Limit (LEL)

read out is relative to the calibrationgas; therefore, may not show actual %

of LEL for use only in normal oxygen

atmospheres

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5% 100%LEL

15%

UEL

Flammable

Range

METHANE

0% 5%

0%LEL

10%

Action Level

0%

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100%

80%

60%

40%

20%

0%

50% 100%0%

xylene

pentane

methane

ACTUAL % LEL

METE

RREADIN

G%

LEL

Relative Response CGI Meter

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% LEL Policy

The employer will issue workpermits when the % LEL is from 0-10% LEL.

When the LEL exceeds 10%,special approval is required inorder for a work permit to be

issued.

For all confined space entrypermits, a 0% LEL is required.

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Toxic Atmosphere Monitors

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Colorimetric Indicator Tubes

Features glass tube with

indicating chemical

chemical specific

contaminated airpumped in at pre-determined rate

Limitations other chemicals may

interfere with result

poor accuracy andprecision

affected by temperatureand humidity

interpretations vary

time consuming - 1 to 30minutes per tube

DETECTOR TUBEPre-filter Color Change

Cotton Plug Indicating Chemical Cotton Plug

on Silica Gel

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Photoionization Detector

Features Nonspecific gas and vapor

detection for organics and someinorganics

Sensitivity is related to the

ionization potential ofcompound

Portable with remote sensingcapabilities

Response time of 90% in lessthan 3 seconds

More sensitive to aromatic andunsaturated compounds thanthe flame ionization detector

Limitations Does not monitor for

specific gases or vapors

Cannot detect Hydrogencyanide or methane

Cannot detect somechlorinated organics

High humidity andprecipitate will negativelyaffect meter response

Photoionization detectors

are calibrated to a singlechemical

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Flame Ionization Detector

FeaturesNonspecific total

hydrocarbon analyzer

Most sensitive tosaturated hydrocarbons

(alkanes), andunsaturated hydrocarbon(alkenes)

Portable with remotesensing probe

Response time of 90% in2 seconds

LimitationsNot suitable for inoganic gases

(e.g. chlorine, hydrogencyanide, ammonia)

Less sensitive to unsaturatedcompounds than PID

Can not use in the presence ofa flammable gas (ignitionsource)

Substances that containsubstituted functional groups(-OH) and (-Cl) reduce thedetector's sensitivity

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Aerosol Monitors

Solids and liquids can becomesuspended in air

light scatter detector

piezoelectric crystal mass monitor

beta attenuation

Total particulate amount

Type not determined

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Suppose prior analysis has established thatthe dust at a certain site contains 5 percentlead and 1 percent arsenic. Duringsubsequent monitoring, the concentration ofdust is found to be 2mg/m3.

(% of each) amount of dust= conc of each

100 present in air

Sample Problem

X

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The concentration of lead and arsenic,

therefore, are calculated to be 0.1 mg/m3

and 0.02 mg/m3 respectively:

0.05 x 2 mg/m3

= 0.1 mg/m3

lead

0.01 x 2 mg/m3 = 0.02 mg/m3 arsenic

Answer

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Combination Instruments

flammable gas and O2

trimeters

four gas meters

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Radiation Monitoring

Alpha

Proportion Counters

Scintillation Counters

Beta and Gamma

Geiger-Mueller Counters

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