| An
air cleaner's effectiveness is measured by how thoroughly
it captures particles and the amount of air it can process
in a given period of time. It's only as good as its ability
to catch particles of all sizes and process enough air to
make a difference.
To this end, the finer the sieve-like action
of a mechanical filter, the smaller the particles it can block.
However, the finer the sieve, the more quickly the filter
will clog up with dust. Though most mechanical filters actually
catch more dust as they become more saturated, airflow grows
increasingly stymied, reducing overall effectiveness.
The best mechanical filters have a very fine
sieve and a large surface area to maximize both dust collection
and airflow.
Filters that use electrical attraction to
grab particles are different. Most don't slow air as they
"fill up," but their charge is diminished by the
accumulation of particles. They're most effective when they're
clean and actually when the air passes through them at a relatively
slow rate.
Dust particles are measured by the micron
(one micron equals 1/25,400 of an inch). The human eye can
see lint, pollen and dust particles larger than 10 microns
(a sharp pencil dot is about 200 microns in diameter).
Most air cleaners eliminate a large percentage
of visible dust that passes through them, but to be really
effective, an air cleaner should eliminate most microscopic
particles, too.
The effectiveness of a filter is tested and
given ASHRAE (American Society of Heating, Refrigeration and
Air-conditioning Engineers) ratings. The first rating, Initial
Staining Dirt Efficiency, is a critical measurement of how
well the filter removes microscopic staining particles such
as tobacco tar, allergens and grease.
The second rating, Average Arrestance Test,
refers to the percentage of ordinary dust, hair, lint and
other large-particulate matter removed. When comparing ratings,
it's important to know which of these two is being listed.
The Association of Home Appliance Manufacturers
(AHAM) certifies some portable air cleaners with a Clean Air
Delivery Rate (CADR). This measures how many cubic feet per
minute (CFM) of air are cleared of a certain size particle.
Three particle sizes are rated: smoke (minute), dust (medium)
and pollen (large).
The higher the CADR rating, the less time
the unit needs to remove a given quantity of certain particles
from a specified room size. AHAM-certified models are marked
with CADR data.
Air
Purifiers | Basic
Types Of Air Purifiers | Your
Whole House Air Purifier |
A
Quick Guide to Air Purifiers |
Quiet
Air Purifier
| Hidden
Dangers: Reduce Toxins in Your Home
|
How
an Air Cleaner Works
| How
Effective Are Home Air Cleaners and Air Purifiers?
|
About
Air Purifiers And Dusting Your Home
| Air
Purifier Ratings |
Using
Car Air Purifiers To Prevent Allergy Symptoms |
