Diffusive monitor test: performance under transient conditions.
Bartley-DL; Deye-GJ; Woebkenberg-ML
Appl Ind Hyg 1987 May; 2(3):119-122
A performance test is presented for passive monitors which must function under conditions where the gas or vapor being determined is present at different concentrations during the time period of the study. Currently both pumped and diffusive samplers are available which provide estimates of time weighted averages (TWA) to assist in the determination of permissible exposure levels of gases or vapors expressed over either 15 minutes or 8 hours. Computation of net bias is described. An example is offered where a performance test was carried out using two groups of nine Palmes tubes each to estimate the TWA concentration of 0.5 hour pulses of nitrogen-oxide (10102440) at instantaneous concentration equal to about 50ppm at both the start and end of 4 hour sampling periods in an exposure chamber. The 95 percent confidence limit was calculated to be 16.9 percent. The authors state that various alternative methods are available for applying such a test and determining the acceptability of a given sampler. The particular test as described can be used to supplement already accepted tests which define the performance of a diffusive sampler by considering temperature, pressure, humidity, ambient air flow, storage time, interferents, and exposure to zero concentration. There is also a NIOSH Standards Completion Program protocol for pump based sampling methods which can be modified to incorporate testing of the diffusive sampler.
NIOSH-Author; Laboratory-testing; Samplers; Sampling-methods; Air-contamination; Air-monitoring; Mathematical-models; Vapors; Equipment-reliability
Applied Industrial Hygiene