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11
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.
2
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.
3
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
4
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
5
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
6
Air Monitoring Instruments Air Monitoring Instruments must bemust be
portable and rugged
easy to operate
7
Air Monitoring Instruments Air Monitoring Instruments must be Inherently Safemust be Inherently Safe
explosion-proof
intrinsically safe
purged
8
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.
9
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.
12
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.
13
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
14
Monitoring EquipmentMonitoring Equipment
Direct-Read Instruments oxygen availability monitor combustibility monitor toxic atmosphere monitor radiation monitor
15
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)
16
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
17
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.
2020
Toxic Atmosphere MonitorsToxic Atmosphere Monitors
21
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
22
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
23
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
24
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
25
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
26
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
27
Combination InstrumentsCombination Instruments
flammable gas and O2
trimeters
four gas meters
28
Radiation MonitoringRadiation Monitoring
Alpha Proportion Counters Scintillation Counters
Beta and Gamma Geiger-Mueller
Counters