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Let's me
start this conversation off by saying we do not live in a 2
dimensional world. If you look at advertising for HEPA air
cleaners and purifiers you see where most talk about the
square footage their machines are rated for. I don't know
about you but my world has height to it making it 3
dimensional.
When trying to
determine what size of air cleaner you need you need to be
concerned about mow many times you need the air changed out
per hour. According to the EPA, Air Changes Per Hour : The
movement of a volume of air in a given period of time. If a
room has 5 air change per hour, it means that the air in the
room will be replaced 5 times in a one-hour period. In most
cases air changes of 6 times per hour is the minimum, 8+ air
changes per hour is really what you want.
First
you need to measure the space you are trying to clean the
air in. Let's say your bedroom is 12 feet wide, 15 feet long
and the ceiling are 9 feet. Based on that (12 X 15 X 8) you
want to clean 1,440 cubic feet of space.
Now
let's say you want to change the air in the room out 6 times
per hour. Take 1,440 (cubic feet of the room) and multiply
by 6 (number of required air changes) and divide by 60. This
tells us we need an air cleaner that moves at least 144 CFM
to clean the room 6 times per hour.
Most of
the smaller HEPA air cleaners move air anywhere from 50-200
CFM and the larger models run 75-560 CFM. Using the example
above an Austin Air Jr running on high (200 CFM) would
change out the air 8.3 times every hour. Realistically
people run their air cleaners on medium most of the time so
you need to take that into consideration.
Other
things you need to take into consideration is the pollutant
source levels and types in the room, noise levels of the air
cleaner and air cleaner placement. Also, HEPA air cleaners
can not clean the air in several rooms at one time.
Stand alone floor units are designed to filter the air in
one room. There are whole house HEPA air cleaners made by
IQAir, Lifebreath, Honeywell and AirPura. These units should
be installed by an air conditioning contractor.
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