The purpose of this study was to evaluate the efficiency of diffusive(or passive) sampler in measuring airborne organic solvents. Diffusive samplers are generally simple in construction and do not require power for operation. The efficiency of the diffusive samplers has not sufficiently been investigated in Korea. Three types of samplers were studied in this study. The sampling and analytical results by passive samplers were compared with results by charcoal tube method recommended by NIOSH(National Institute for Occupational Softy and Health).
The following characteristics are identified and studied as critical to the performance passive monitors; recovery, reverse diffusion, storage stability, accuracy and precision, face velocity and humidity. n-Hexane, TCE(trichloroethylene) and toluene were used as test vapors. A dynamic vapor exposure system consisting of organic vapor generator and sampling chamber for evaluating diffusive samplers are made.
The results of the study are summarized as follows.
1. NIOSH recommends that the overall accuracy of a sampling method in the range of 0.5 to 2.0 times the occupational health standard should be ±25 percent for 95 percent confidence level. Among three types of diffusive sampler, sampler A has permeation membrane and samplers B and C have, diffusive areas, samplers A and B met the criterion that overall accuracy for 95% confidence level of the samplers were within ±25 percent of the reference value. Sampler C had overall accuracy ±9.6% and ±11.8% in hexane and TCE, respectively. The concentration of toluene was overestimated in sampler C with overall accuracy of 43.9%.
2. The desorption efficiencies of diffusive samplers were 96-107%.
3. There was no significant sample loss during four weeks of storage both with and without refrigeration.
4. There was no significant reverse diffusion, when the samplers were exposure to clean air for 2 hours after sampling for 2 hours at the level of 2 TLV.
5. In case of 8 hours sampling, relative differences(RD) of concentrations between charcoal tube method and diffusive method were 15-39%, 13-46%, and 4-35% for sampler A, B and C, respectively. The performance was poor in 8 hours sampling for multiple substance monitors.
6. At high velocity(100 ㎝/sec), samplers B and C overestimated the concentrations of organic vapors, and sampler A with permeation membrance gave better results.
7. At 80% relative humidity, samplers showed no significant effect. Low humidity also did not affect the diffusive samplers.
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