Environmental Engineering Reference
In-Depth Information
Figure 12.14
Effect of the operation of an in-duct electronic air cleaner on measured
tobacco particle concentration in a residence. (From McNall, P.E.,
Arch. Environ.
Health
, 30, 552, 1975. With permission.)
surgical staff. Typically, surgical rooms use a combination of HEPA filters and
laminar air flow. In one study of a surgery room operated at an air exchange
rate of 20 ACH, culturable/viable bacterial levels were observed to decrease
by approximately 89% when the system was operated under empty-room
conditions and approximately 88% while surgery was in progress.
Air cleaners have been evaluated relative to their potential for reducing
airborne mold levels in residences. In a study of culturable/viable airborne
mold levels in residences, investigators observed significant reductions in
total culturable/viable mold counts in residences using in-duct electronic
air cleaners. Average reductions in 21 residences were approximately 77%
(with a range of 66 to 87%) when the system was operated continuously and
50% (with a range of 0 to 83%) when the air cleaner was operated intermit-
tently. The author has observed reductions in total airborne mold levels
(viable and nonviable mold spores and particles) of 90% in a single-family
residence using an extended-media filter.
In another study, cat allergen levels were reduced by 38% on the main
level and 4% in the basement of a house with an in-duct HEPA filter when
the blower system was operated continuously. Air cleaning appeared to be
relatively ineffective when a significant active allergen-producing source
(two cats) was present.
 
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