A Field Comparison of Volatile Organic Compound Measurements Using Passive Organic Vapor Monitors and Stainless Steel Canisters

Abstract

Concurrent field measurements of 10 volatile organic compounds (VOCs) were made using passive diffusion-based organic vapor monitors (OVMs) and the U.S. Federal Reference Method, which comprises active monitoring with stainless steel canisters (CANs). Measurements were obtained throughout a range of weather conditions, repeatedly over the course of three seasons, and at three different locations in the Minneapolis/St. Paul metropolitan area. Ambient concentrations of most VOCs as measured by both methods were low compared to those of other large metropolitan areas. For some VOCs a considerable fraction of measurements was below the detection limit of one or both methods. The observed differences between the two methods were similar across measurement sites, seasons, and meteorological variables. A Bayesian analysis with uniform priors on the differences was applied, with accommodation of sometimes heavy censoring (nondetection) in either device. The resulting estimates of bias and standard deviation of the OVM relative to the CAN were computed by tertile of the canister-measured concentration. In general, OVM and CAN measurements were in the best agreement for benzene and other aromatic compounds with hydrocarbon additions (ethylbenzene, toluene, and xylenes). The two methods were not in such good agreement for styrene and halogenated compounds (carbon tetrachloride, p-dichlorobenzene, methylene chloride, and trichloroethylene). OVMs slightly overestimated benzene concentrations and carbon tetrachloride at low concentrations, but in all other cases where significant differences were found, OVMs underestimated relative to canisters. Our study indicates that the two methods are in agreement for some compounds, but not all. We provide data and interpretation on the relative performance of the two VOC measurement methods, which facilitates intercomparisons among studies.

Predictors of personal air concentrations of chloroform among US adults in NHANES 1999–2000

“…To obtain stable P-values in weighted regression, the maximum number of estimable parameters is limited to the denominator degrees of freedom of the variance estimator (i.e., the number of primary sampling clusters minus the number of sampling strata) (Research Triangle Institute, 2001 Chung et al (1999), comparing passive samplers to canister whole-air samplers suggests negative bias for the passive samplers, but further states that differences are likely less than 25%. More recently, Pratt et al (2005) have conducted a comparison of passive samplers similar to those used in NHANES and canister whole-air samplers for VOCs and support the small bias conclusion of Chung et al (1999). Both of these studies involved laboratory and field components, but not personal monitoring.…”

Spatial Analysis of Volatile Organic Compounds from a Community-Based Air Toxics Monitoring Network in Deer Park, Texas, USA

“…Thus, in descending order of preference, OVMs were placed (1) in a covered porch area, (2) under the eaves of the house, and (3) in a covered carport area. This resulted in four eave locations, five (Chung, Morandi, Stock, & Afshar, 1999;Chung et al, 2004;Mukerjee et al, 2004;Pratt et al, 2005;Weisel et al, 2005) and has been used extensively elsewhere (Cohen et al, 1990;Ware et al, 1993;Sexton et al, 2004). Quantitative analysis for a target list of 31 VOCs was performed by means of solvent extraction of OVM charcoal badges followed by gas chromatography/mass spectrometry (GC/MS).…”

Ventilation and indoor air quality in retail stores: A critical review (RP-1596)

“…Depending on the compound sampled, organic vapor monitors have been reported to underestimate (Stock et al 1999) or overestimate (Pratt et al 2005) concentrations when compared to canisters. Dobos (2000) reported that styrene concentrations measured by organic vapor monitors were 31% higher than measurements from sorbent tubes.…”