White Paper

Electrostatic precipitators
Electrostatic precipitators charge particles electrically with either a
positive or negative charge. The particles are then attracted and
retained by oppositely charged collection plates
9
(fig. 2).
Air cleaners using electrostatic precipitators are good in clean-
ing the air with low noise while consuming little energy. However,
electrostatic forces are not very efficient in collecting large and
heavy particles. The unit also needs regular cleaning and because
of the high voltage ionize fields, electrostatic air cleaners often
emit ozone as by-product. Ozone is deemed to be hazardous to
human health and scientifically there is no safe concentration limit.
So even if the emission is below public health standards it can still
be harmful. Ozone can also react with chemical emissions creating
chemical compounds with detrimental health effects. Despite its
toxicity, ozone can still function as an odor reducer, which neither
electrostatic nor mechanical filtration alone can. However, this is not
a preferable way.
10
The recommended non-toxic way to reduce odors is to use adsor-
bent material such as activated carbon. Activated carbon is a natural
material for air filter and has a very porous structure that can adsorb
gaseous pollutants including odors.
+
+
-
-
-
-
+
+
negatively
charged particle
positively
charged particle
uncharged particle
Fig 2
Charged particles are attracted to the oppositely charged collector plates while un-
charged particles only pass the plates.
particles
1
1
2
2
3
3
9
http://www.epa.gov/apti/course422/ce6a1.html
10
http://www.epa.gov/iaq/pubs/ozonegen.html