A study on comparison of standard charcoal tube method, infrared gas analyzer, and detector tube method were conducted. Measurements were performed simultaneously at same sampling points in an air chamber containing benzene, toluene and xylene vapors. Charcoal tube samples were collected at sampling flowrates of 0.05, 0.2, 0.5, and 1.0 lpm.
Results are as follows :
1. Coefficients of variation of results with charcoal tube method for benzene, toluene and xylene mixture vapor were 14.34 % in benzene(0.28-11.12 ppm), 9.20 % in toluene (2.68-135.09 ppm) and 10.21 % in xylene (2.56-82.64 ppm), respectively.
2. Results of infrared gas analyzer in mixture air were non-specific on benzene and toluene. Ratio of results of infrared gas analyzer to those of charcoal tube on benzene, toluene and xylene were 696.4 %, 30.3 % and 36.6 %, respectively.
3. Ratio of responses of detector tubes to those of charcoal tube were 49.4 % in benzene, 22.1 % in toluene and 223.9 % in xylene. Xylene detector tube were interfered by toluene greatly.
4. Collection efficiencies of charcoal tubes at low concentration(benzene : 1 ppm, toluene : 10 ppm, xylene : 10 ppm) were stable on various flowrate from 0.05 to 1.0 lpm, but at high concentrations the efficiency decreased at high flowrate above 0.5 1pm.
5. Within the saturation capacity of charcoal, collection effiency decreased at 0.5-1.0 1pm. Sampling feowrates of 0.05-0.20 1pm were appropriate for sampling organic vapors.
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