of Air Filters
WHAT ARE FILTERING
Filtering devices are either central filtration (often called "in-duct") systems
put into the heating, ventilation, and air conditioning (HVAC) system of a home or
portable units with an attached fan to assist in reducing indoor atmospheric pollutants.
MECHANICAL draw atmosphere through a flat, pleated or high efficiency particulate HEPA
surface to trap particles. HEPA Filtration is the most efficient mechanical device for
removing small particles which can be breathed deeply into the lungs. The highest
efficiency cleaners, widely available today, remove 0.3 micron (1 micron = 1 millionth of
a meter) sized particles at a minimum of 99.97% efficiency.
ELECTRONIC, in their
simplest form, include negative ion generators that charge airborne particles so they
become attracted to and settle on room surfaces. Activity within a room, however, may stir
up and release the settled particles back into the environment. More effective units
called electrostatic precipitators electrically charge airborne particles and then trap
them on oppositely charged metal plates. These plates must be cleaned regularly for proper
HYBRIDS are made up of
two or more of the above sifters. An example is the "electret" which uses
electrically charged flat or pleated fabric to attract airborne particles. These are
efficient when clean, but as they fill with particles the efficiency decreases and they
must be replaced.
GAS PHASE are often
attached to filtration systems to remove specific gases, vapors and odors.
HOW DO I CHOOSE?
"CENTRAL FILTRATION SYSTEM VS. PORTABLE DEVICE"
units are used when cleaning is desired in a room. Central filtration systems are used
when whole-house environment cleaning is needed. However, these systems require that the
central heating or air conditioning fan be "on" in order for filtration to
The efficiency of these systems is measured in terms of the particle size that the device
can capture. In most cases, very small particles are the ones that penetrate deep into the
lungs, causing health problems. Look for mechanical cleaners such as HEPA filters and
electronic filtration systems that can effectively trap large and small particles.