Concentrations and sources of VOCs for the CHBS
Concentrations of 39 frequently encountered VOCs were measured indoors and outdoors at each of the CHBS buildings (Daisey et al., 1994). The VOCs were collected on multisorbent samplers over an 8-hour workday. The samplers were analyzed for individual VOCs by thermal desorption gas chromatography/mass spectrometry (GC/MS) and for total VOCs (TVOC) by flame-ionization detector. The VOC data was analyzed to characterize indoor exposure concentrations, to investigate inter-building variations in chemical composition and concentrations, and to help identify major sources of VOC exposure. The geometric mean (GM) indoor concentrations, the geometric standard deviations and the concentration ranges in parts per billion (ppb) for the individual VOCs are presented in Table 2. Concentrations of TVOC (in micrograms per cubic meter or µg/m³) also are shown along with the ranges of the indoor/outdoor concentration ratios.

VOCs predominantly from indoor or outdoor sources in the CHBS
A compound was defined as coming predominantly from indoor sources if its indoor/outdoor concentration ratio was greater than 1.35 in 8 or more of the 12 buildings. These compounds included dichloromethane (methylene chloride), trichloroethylene, 1,1,1-trichloroethane, ethanol, isopropanol, acetone, pentanal, hexanal, limonene and n-dodecane. Conversely, a compound was defined as coming predominantly from outdoor sources if its indoor/outdoor ratio was less than 1.35 in 8 or more buildings. Many of the aromatic hydrocarbons and more volatile aliphatic hydrocarbons, such as benzene, toluene, xylenes, ethyltoluenes, trimethylbenzenes, n-pentane and 3-methylhexane mainly came from outdoor motor vehicle exhaust emissions. Tetrachloroethylene came from outdoor dry-cleaning sources.