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FIGURE 15.11 Concentrations of HCHO,HCOOH, and CH3OH measured using long-path FTIR in a mobile home as a function of temperature. Although the gas stove burners were on, these were shown in separate experiments not to be the source of these organics (adapted from Pitts et al., 1989.)

HCOOH has also been observed from outgassing in a mobile home trailer by chemical ionization mass spectrometry during measurements of HNO-, (Huey et al., 1998) and at lower concentrations (mean of fO ppb) in conventional homes (Reiss et al., 1995a).

Figure 15.12 summarizes the ratio of indoor-to-outdoor concentrations of HCHO and higher aldehydes as well as formic and acetic acids measured in some conventional homes. Concentrations of all of these compounds, except possibly propionaldehyde, are significantly higher indoors, suggesting that not only

HCHO but higher aldehydes and ketones as well as acids have significant indoor sources (Lewis and Zweidinger, f992; Zhang et al., 1994a, 1994b; Zhang and Lioy, 1994; Reiss et al., 1995a). As discussed later, reactions of hydrocarbons with ozone indoors is a potential source, in addition to direct emissions.

It should be noted that while building materials are sources of a variety of VOCs, they can also adsorb organics as well (e.g., Van Loy et al., 1997). As a result, building surfaces and contents may act as reservoirs of organics, slowly releasing compounds over a period of time.

Anthropogenic activities. There are many sources of VOCs associated with human activities in buildings. For example, mixtures of C10 and Cn isoparaffinic hydrocarbons, which are characteristic of liquid process copiers and plotters, have been identified in office buildings in which these instruments were in use (Hodgson et al., 1991). Emissions of a number of hydrocarbons and aldehydes and ketones have been observed during operation of dry-process copiers; these include significant emissions of ethylbenzene, 0-, m-, and /ยป-xylenes, styrene, 2-ethyl-I-hexanol, acetone, n-nonanal, and benzaldehyde (Leovic et al., 1996). Enhanced levels of acetaldehyde in an office building in Brazil were attributed to the oxidation of ethanol used as a cleaning agent (Brickus et al., f998), although levels outdoors were also enhanced due to the use of ethanol as a fuel (see Chapter f6.D.4). Pyrocatechol has been measured in an occupational environment where meteorological charts are mapped on paper impregnated with this compound (Ekinja et al., f 995), and

Time (PST)

FIGURE 15.11 Concentrations of HCHO,HCOOH, and CH3OH measured using long-path FTIR in a mobile home as a function of temperature. Although the gas stove burners were on, these were shown in separate experiments not to be the source of these organics (adapted from Pitts et al., 1989.)

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