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

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air monitoring

Air Monitoring

Instructional Goal:

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

sampling methods
Sampling 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.
instantaneous sample
Instantaneous 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
air monitoring data is used to
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
sampling system
Sampling 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
air monitoring instruments must be
Air Monitoring Instruments must be
  • portable and rugged
  • easy to operate
air monitoring instruments must be inherently safe
Air Monitoring Instruments must be Inherently Safe
  • explosion-proof
  • intrinsically safe
  • purged
air monitoring instruments must give reliable and useful results
Air Monitoring Instruments must give Reliable and Useful Results
  • 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.
air monitoring instruments must give reliable and useful results9
Air Monitoring Instruments must give Reliable and Useful Results
  • 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.
air monitoring instruments must give reliable and useful results10
Air Monitoring Instruments must give Reliable and Useful Results
  • 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.
air monitoring instruments must give reliable and useful results11
Air Monitoring Instruments must give Reliable and Useful Results
  • Accuracy
    • the relationship between a true value (i.e., the actual concentration of a contaminant) and the instrument reading.
air monitoring instruments must give reliable and useful results12
Air Monitoring Instruments must give Reliable and Useful 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.
bench calibration
  • 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
monitoring equipment
Monitoring Equipment
  • Direct-Read Instruments
    • oxygen availability monitor
    • combustibility monitor
    • toxic atmosphere monitor
    • radiation monitor
oxygen indicators
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)
combustible gas monitor
Combustible 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
relative response cgi meter
Relative Response CGI Meter















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.
colorimetric indicator tubes
Colorimetric Indicator Tubes


glass tube with indicating chemical

chemical specific

contaminated air pumped in at pre-determined rate


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

photoionization detector
Photoionization Detector


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


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

flame ionization detector
Flame Ionization Detector


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


Not 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

aerosol monitors
Aerosol Monitors
  • Solids and liquids can become suspended in air
    • light scatter detector
    • piezoelectric crystal mass monitor
    • beta attenuation
  • Total particulate amount
  • Type not determined
sample problem
Sample Problem

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)amount of dust= conc of each

100 present in air



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

combination instruments
Combination Instruments
  • flammable gas and O2
  • trimeters
  • four gas meters
radiation monitoring
Radiation Monitoring
  • Alpha
    • Proportion Counters
    • Scintillation Counters
  • Beta and Gamma
    • Geiger-Mueller Counters