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
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.