Points to Consider

CADR/Filter Efficiency
Buyers need not rely solely on a manufacturer’s efficiency
claims. Make sure that the unit’s performance is third-party
tested also.
The Clean Air Delivery Rate (CADR) program is sponsored by
the Association of Home Appliance Manufacturers (AHAM),
an independent industry organisation. It measures the total
volume of air that a particular air purification system cleanses
of a specific pollutant in one minute. CADR test results can
be converted to cubic metres per hour (m
3
/h), with a number
rating for three “yardstick” particles: tobacco smoke, dust and
pollen. The higher the CADR test numbers, the better the unit’s
overall ability to clean indoor air.
All results of tested air purifiers’ overall room air cleaner
performance tests are published. AHAM’s performance tests
are recognised as accurate and impartial by the EPA and the
American Lung Association. Ratings can be found online at
www.cadr.org.
Capacity
After filter efficiency, air volume capacity is key to selecting
the best in-room air cleaner. The unit must be rated to handle
the total volume of air in the room where it operates. As air is
constantly bombarded by pollutants, the air purifier must be
able to remove them at the same rate as they enter to be effec-
tive. This value is expressed as recommended room size and
should be based on that the unit can make 5 air changes per
hour.
Simply measure the room’s length and width, multiply to obtain
the room size, and compare with AHAM recommendations.
But be sure to include ceiling height in estimating the unit’s air
processing capability. Ceiling height makes a big difference in
the cubic metres of a room. AHAM room size assumes a 2.4
metre ceiling. If you have high ceilings, the extra step is critical
to choosing an air cleaner with adequate capacity for the room.
Now compare your result to the AHAM recommendations.
Specific Health Concerns
With the exception of allergens and airborne pathogens, the
size of a given particle determines the degree of potential threat
to human health. Different air filtration processes have varying
effectiveness in removing different contaminants. It is therefore
important to identify which pollutants you want to eliminate.
Generally, airborne particles are categorized by the EPA as
small (0.1 to 0.3 micron), mid-range (0.3 to 0.9 micron) and
large (1.0 micron or larger).
Mid-Range Particles
Mid-range particles (0.3 to 0.9 micron) include house and tex-
tile dust, pet dander, dust mites and their feces, many bacteria,
auto exhaust, mold spores, and particles from laser printers
and copiers.
Particles of this size present the greatest health concern
because they are small enough to get past the cilia in the nasal
passages but too large to be easily exhaled. Particles in this
size range are more likely to become lodged in lung tissue
and are suspect in a wide range of health problems related to
indoor air pollution, from headaches and dizziness to cardio-
vascular disease and cancer.
Look for an air filter with high efficiency for mid-range particles
when respiratory conditions are present, when allergens are a
concern, and when asthma is triggered by pet dander, mold,
or dust mite allergen. HEPA filters generally capture mid-range
particles, although efficiency varies among makes and models.
Small Particles
Small particles (0.1 to 0.3 micron) include many viruses, bac-
teria and exhaust particles. Although these small particles are
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