potential to dilute and remove indoor-generated pollutants, yet without proper filtration, it
can increase indoor air pollution from outdoor sources depending on weather conditions
and outdoor air quality.
CHANGES IN OCCUPANT BEHAVIOR
Increased Air Conditioning Usage
The Department of Energy’s U.S. Energy Information Administration also
reported that the percent of homeowners with central air conditioning who indicated
using air conditioning "all summer long" increased from 33% to 52% between 1978 and
1997, respectively (DOE 2010). Not surprisingly, the southern portion of the United
States had the highest percentage (69%) of homeowners with central air conditioning in
1997 who reported using it “all summer long”. As outdoor temperatures and allergens
increase, air conditioner usage will undoubtedly increase, which will in turn adversely
increase the concentrations of some indoor air pollutants.
Changes in Temporal Mobility (Activity Patterns)
Several studies performed in California have shown that individuals as early as
the late 1980s and early 1990s spent a significant amount (87%) of their time indoors
(Klepsis et al. 2001, Jenkins et al. 1992). These percentages were fairly constant over
the various regions of the United States for that time period (Klepsis et al. 2001, Field et
al. 1998). Residential occupancy comprises the majority (generally over 65%) of the
time spent indoors (Klepsis et al. 2001, Field et al. 1998, Jenkins et al. 1992) with
individuals more vulnerable to air pollution (e.g., children and the elderly) spending even
a greater percentage of time in the home (Field et al. 1998, Liu et al. 1993). The EPA’s
Consolidated Human Activity Database (CHAD) may be a useful resource for
determining if time spent indoors continues to increase as outdoor temperatures
increase.
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