Presentation on theme: "1 1 Air Monitoring Instructional Goal: Enable participants to recognize the value of direct-reading instruments in providing immediate air concentration."— Presentation transcript:
1 1 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.
2 Sampling Methods < Area sampling Finvolves placing collection devices within designated areas and operating them over specific periods of time. < Personal sampling Finvolves collecting samples from within the breathing zone of an individual, sometimes by the individual wearing a sampling device.
3 Instantaneous Sample < are collected over brief periods of time Fgrab-type sample Fexamines stable contaminant concentrations or peak levels of short duration. Frequire highly sensitive analytical methods due to the small sample volume
4 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
5 Sampling System < sampling instrument or system chosen depends on a number of factors: Finstrument or system efficiency Foperational reliability Fease of use and portability Favailability of the instrument and component parts Finformation or analysis desired Fcalibration requirements
6 Air Monitoring Instruments must be < portable and rugged < easy to operate
7 Air Monitoring Instruments must be Inherently Safe < explosion-proof < intrinsically safe < purged
8 Air Monitoring Instruments must give Reliable and Useful Results < Response time Fis 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 must give Reliable and Useful Results < Sensitivity Fdefined as the ability of an instrument to accurately measure changes in concentration. Sensitive instruments can detect small changes in concentration. FIt is important to use an instrument with an operating range that will measure the ambient concentrations on-site.
10 Air Monitoring Instruments must give Reliable and Useful Results < Selectivity F the ability of an instrument to detect and measure a specific chemical or group of similar chemicals. F Interferences from other chemicals can affect the accuracy of the instrument reading by producing a similar response.
11 Air Monitoring Instruments must give Reliable and Useful Results < Accuracy Fthe relationship between a true value (i.e., the actual concentration of a contaminant) and the instrument reading.
12 Air Monitoring Instruments must give Reliable and Useful Results < Precision Fa statistical measurement of an instrument's ability to reproduce a reading. FWhen 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 Bench Calibration < follow manufacturers 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
15 Oxygen Indicators < 20.8% O 2 is normal air < at and below 19.5% O 2 in air, O 2 deficient Feither displaced by another gas For consumed by combustion or reaction 23% O 2 in air, increased risk of combustion (possible oxidizer present)
16 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
100% 80% 60% 40% 20% 0% 50% 100% 0% xylene pentane methane ACTUAL % LEL METER READING % LEL Relative Response CGI Meter
19 % 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.
20 Toxic Atmosphere Monitors
21 Colorimetric Indicator Tubes < Features Fglass tube with indicating chemical F chemical specific Fcontaminated air pumped in at pre- determined rate < Limitations Fother chemicals may interfere with result Fpoor accuracy and precision Faffected by temperature and humidity Finterpretations vary Ftime consuming - 1 to 30 minutes per tube
22 Photoionization Detector < Features FNonspecific gas and vapor detection for organics and some inorganics FSensitivity is related to the ionization potential of compound FPortable with remote sensing capabilities FResponse time of 90% in less than 3 seconds FMore sensitive to aromatic and unsaturated compounds than the flame ionization detector < Limitations FDoes not monitor for specific gases or vapors FCannot detect Hydrogen cyanide or methane FCannot detect some chlorinated organics FHigh humidity and precipitate will negatively affect meter response FPhotoionization detectors are calibrated to a single chemical
23 Flame Ionization Detector < Features FNonspecific total hydrocarbon analyzer FMost sensitive to saturated hydrocarbons (alkanes), and unsaturated hydrocarbon (alkenes) FPortable with remote sensing probe FResponse time of 90% in 2 seconds < Limitations FNot suitable for inoganic gases (e.g. chlorine, hydrogen cyanide, ammonia) FLess sensitive to unsaturated compounds than PID FCan not use in the presence of a flammable gas (ignition source) FSubstances that contain substituted functional groups (-OH) and (-Cl) reduce the detector's sensitivity
24 Aerosol Monitors < Solids and liquids can become suspended in air Flight scatter detector Fpiezoelectric crystal mass monitor Fbeta 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/m 3. (% of each)amount of dust= conc of each (% of each) amount of dust= conc of each 100 present in air Sample Problem X
26 The concentration of lead and arsenic, therefore, are calculated to be 0.1 mg/m 3 and 0.02 mg/m 3 respectively: 0.05 x 2 mg/m 3 = 0.1 mg/m 3 lead 0.01 x 2 mg/m 3 = 0.02 mg/m 3 arsenicAnswer
27 Combination Instruments < flammable gas and O 2 < trimeters < four gas meters