1 1 Air Monitoring Instructional Goal: Enable participants to recognize the value of direct-reading...

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Air MonitoringAir Monitoring

Instructional Goal: Enable participants to recognize the value of direct-reading instruments in providing immediate air concentration results at a hazardous waste site.

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Sampling MethodsSampling Methods

Area sampling involves placing collection devices within

designated areas and operating them over specific periods of time.

Personal sampling involves collecting samples from within the

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

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Instantaneous SampleInstantaneous Sample

are collected over brief periods of time grab-type sample examines stable contaminant

concentrations or peak levels of short duration.

require highly sensitive analytical methods due to the small sample volume

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Air Monitoring Data is Air Monitoring Data is used toused 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 SystemSampling System

sampling instrument or system chosen depends on a number of factors:

instrument or system efficiency operational reliability ease of use and portability availability of the instrument and

component parts information or analysis desired calibration requirements

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Air Monitoring Instruments Air Monitoring Instruments must bemust be

portable and rugged

easy to operate

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Air Monitoring Instruments Air Monitoring Instruments must be Inherently Safemust be Inherently Safe

explosion-proof

intrinsically safe

purged

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Air Monitoring Instruments Air Monitoring Instruments must give Reliable and Useful must give Reliable and Useful ResultsResults

Response time is the length of time the monitor takes

from when it "senses" a contaminant until it generates data. For direct-reading instruments, response times may range from a few seconds to several minutes.

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Air Monitoring Instruments Air Monitoring Instruments must give Reliable and Useful must give Reliable and Useful ResultsResults

Sensitivity defined as the ability of an instrument to accurately

measure changes in concentration. Sensitive instruments can detect small changes in concentration.

It is important to use an instrument with an operating range that will measure the ambient concentrations on-site.

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Air Monitoring Instruments Air Monitoring Instruments must give Reliable and Useful must give Reliable and Useful ResultsResults

Selectivity the ability of an instrument to detect and

measure a specific chemical or group of similar chemicals.

Interferences from other chemicals can affect the accuracy of the instrument reading by producing a similar response.

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Air Monitoring Instruments Air Monitoring Instruments must give Reliable and must give Reliable and Useful ResultsUseful Results

Accuracy the relationship between a true value

(i.e., the actual concentration of a contaminant) and the instrument reading.

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Air Monitoring Instruments Air Monitoring Instruments must give Reliable and must give Reliable and Useful ResultsUseful Results Precision

a statistical measurement of an instrument's ability to reproduce a reading.

When an instrument does not receive routine maintenance the precision of the readings may change (become more random) this can affect the amount of error in the data collected.

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BenchBench CalibrationCalibration

follow manufacturer’s directions for calibration to ensure accurate field data

use standard sample of known concentration for calibration

adjust the instrument read-out so that it corresponds to the actual concentration

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Monitoring EquipmentMonitoring Equipment

Direct-Read Instruments oxygen availability monitor combustibility monitor toxic atmosphere monitor radiation monitor

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Oxygen IndicatorsOxygen Indicators

20.8% O2 is normal 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 MonitorCombustible Gas Monitor

measures concentration of flammable vapor or gas in air

reads in % Lower Explosion Limit (LEL)

read out is relative to the calibration gas; therefore, may not show actual % of LEL

for use only in normal oxygen atmospheres

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5% 100%LEL

15%UEL

FlammableRange

METHANE

0% 5%

0%LEL

10%

Action Level

0%

100%

80%

60%

40%

20%

0%50% 100%0%

xylene

pentane

methane

ACTUAL % LEL

ME

TE

R R

EA

DIN

G %

LE

LRelative Response CGI MeterRelative Response CGI Meter

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% LEL Policy% LEL Policy

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

When the LEL exceeds 10%, special approval is required in order for a work permit to be issued.

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

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Toxic Atmosphere MonitorsToxic Atmosphere Monitors

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Colorimetric Indicator TubesColorimetric Indicator Tubes

Features glass tube with

indicating chemical

chemical specific

contaminated air pumped in at pre-determined rate

Limitations other chemicals may

interfere with result poor accuracy and

precision affected by temperature

and humidity interpretations vary time consuming - 1 to

30 minutes per tube

DETECTOR TUBE Pre-filter Color Change

Cotton Plug Indicating Chemical Cotton Plug on Silica Gel

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Photoionization DetectorPhotoionization Detector Features

Nonspecific gas and vapor detection for organics and some inorganics

Sensitivity is related to the ionization potential of compound

Portable with remote sensing capabilities

Response time of 90% in less than 3 seconds

More sensitive to aromatic and unsaturated compounds than the flame ionization detector

Limitations Does not monitor for

specific gases or vapors Cannot detect

Hydrogen cyanide or methane

Cannot detect some chlorinated organics

High humidity and precipitate will negatively affect meter response

Photoionization detectors are calibrated to a single chemical

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Flame Ionization DetectorFlame Ionization Detector Features

Nonspecific total hydrocarbon analyzer

Most sensitive to saturated hydrocarbons (alkanes), and unsaturated hydrocarbon (alkenes)

Portable with remote sensing probe

Response time of 90% in 2 seconds

LimitationsNot suitable for inoganic gases

(e.g. chlorine, hydrogen cyanide, ammonia)

Less sensitive to unsaturated compounds than PID

Can not use in the presence of a flammable gas (ignition source)

Substances that contain substituted functional groups (-OH) and (-Cl) reduce the detector's sensitivity

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Aerosol MonitorsAerosol Monitors

Solids and liquids can become suspended 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 that the dust at a certain site contains 5 percent lead and 1 percent arsenic. During subsequent monitoring, the concentration of dust is found to be 2mg/m3.

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

100100 present in airpresent in air

Sample ProblemSample 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

AnswerAnswer

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Combination InstrumentsCombination Instruments

flammable gas and O2

trimeters

four gas meters

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Radiation MonitoringRadiation Monitoring

Alpha Proportion Counters Scintillation Counters

Beta and Gamma Geiger-Mueller

Counters