I want to put a HEPA filter in my A/C Air Return Grille. I check local
big box stores and didn't find anything. Strike-out at local A/C
suppliers such as Michael.
I did a google search "HEPA Air Return Filters" and got essentially
nothing. Some sponsored links were promising, but I wasn't able find
anything there either.
Is this not a commonly available type of filters? Are they not
recommended for some reason? Can someone recommend an (online) place to
Sounds like something that would restrict air flow and screw up the
operation of your system. If you have a proper filter on the blower, I
don't see that you'd gain anything putting more filters on the return.
Most residential air handlers are not designed to be used with any
filter that restricts the air flow more than the cheap one dollar
filter. Restricting the air flow could cause the evaporator to freeze
creating a vicious cycle of further restriction of the air flow.
Lately it has become a good money making gimmick for the hardware
stores to sell expensive air filters to the uninformed. If you insists
on using any other type of filer first make sure that there is some
way that you can observe the evaporator. Is there some kind of access
cover that you can remove to make sure it isnt freezing? If so then
check it every few hours. If it freezes it will look like one of those
old refrigerators that you had to manually defrost. If it doesnt
freeze then youre ok.
The real gimmic are the fiberglass filters that let 95% of dirt
through and degrade system performance by clogging up coils. My
neighbor had to remove his AC coil one winter, he got no heat it was
clogged shut, next spring he power washed it. A properly designed
system and ductwork can handle a 3M filtrete filter, if it cant its an
airflow problem possibly from poor ductwork design. For a Hepa filter
on a standard homes AC the filter might need to be the size the air
handler to give it proper airflow , the filters would cost 100$ to
replace. I use a 4" pleated merv 10 Honeywell replacement filter that
doesnt reduce airflow and doesnt even have to be changed every year
since the surface filtering area is very large, maybe 30-40 sq ft. My
4" media is recommended by my Space Pack manufacturer.
I've often wondered why today's so-called high-efficiency furnaces don't
include a seasonal bypass duct so that during winter operation air can
flow around the AC coil instead of needlessly being forced through it.
To get one that would fit you wouldnt have enough airflow to run the
system properly it would be so restrictive, a retrofit might cost 1000
with a 100$ filter, im just guessing on prices, and the filters size
would be huge to not restrict airflow. You only need to protect the
equipment, a hepa would be overkill for that. Do research on Merv
ratings, Honeywell, 3M and others have alot of information at their
The 3M Filtrete 1900 MER filters are about the highest filtration you
will find in standard residential HVAC return filter sizes and which
won't produce an excessive airflow restriction and harm the system.
True HEPA filters would be available to fit the ventilation units used
by the asbestos abatement folks, but you would likely need to rework
your return to increase the return filter area in order to be able to
use those filters without excessive airflow restriction which will harm
your system. They are also expensive.
Suggest sticking to the Filtrete filters, they aren't far behind HEPA
and your system probably has too many leaks at duct joints for a true
HEPA filter to matter.
First you would need a system designed for HEPA air filters. These filters
can be 4 inches thick! You would also want a regular prefilter.
Hospitals use these as the filters are so fine, they can filter airborn
bacteria out of the air. Mechanical contractors would install these systems.
Search google.com for the terms...
Mechanical contractor HVAC
Also you can get stand alone HEPA air cleaners at Walmart.
HEPA filters are very specialized and have absolutely no place in the
home. Basically, it's become the new marketing scam aimed at rubes.
HEPA filters filter such small particles, they are used in "clean
rooms", where micron sized particles are verboten. You have to build
a specialized room where outside ventilation is strictly controlled
and people wear clean-room bunny suits and the interior air is
constantly recycled through HEPA filtered whole and partial filtering
systems. Even the floors are part of the filtering system. The cost
of these rooms is staggering.
Anything claiming to be HEPA for your HVAC or vacuum cleaner is complete
You do seem to relish being *boldly* ignorant--
Just to keep it easy- here's a copy/paste from Wikipedia-
"The original HEPA filter was designed in the 1940s and was used in
the Manhattan Project to prevent the spread of airborne radioactive
contaminants. It was commercialized in the 1950s, and the original
term became a registered trademark and a generic term for highly
efficient filters. Over the decades filters have evolved to satisfy
the higher and higher demands for air quality in various high
technology industries, such as aerospace, pharmaceutical processing,
hospitals, health care, nuclear fuels, nuclear power, and electronic
microcircuitry (computer chips).
Today, a HEPA filter rating is applicable to any highly efficient air
filter that can attain the same filter efficiency performance
standards as a minimum and is equivalent to the more recent NIOSH N100
rating for respirator filters. The United States Department of Energy
(DOE) has specific requirements for HEPA filters in DOE regulated
applications. Products that claim to be "HEPA-type", "HEPA-like", or
"99% HEPA" do not satisfy these requirements and may not have been
tested in independent laboratories."
I'll grant you that Wikipedia is a pretty shake source-- so I welcome
anything other than your opinion on the matter.
You've worked how many hours in a true clean room. You've set up and
designed systems in how many class 1000/100 clean rooms? Do you know
how big a .3-5 micron particle is? Do you know how much HEPA
circulation surface/capacity is required for a given volume of space to
achieve ANY level of HEPA classification? You've certified how many
environments for particulate levels?
Hell, even the first clean room I worked in was a joke. After initial
design, setup, and qualification, it degenerated into nothing more
than a visual sales gimmick to impress potential customers. Looked
good through the conveniently located viewing windows, but never again
acheived anything remotely close to what a true HEPA filter is
designed to do.
Putting a true HEPA filter in your home furnace/central AC or vacuum
cleaner is like dropping a 5 gal home aquarium filter in an outdoor
swimming pool. IOW, totally useless. You can call it what you like
but real HEPA filters are only truly effective in VERY closed and
controlled environments. You wanna pay big bucks for a HEPA filter
while tons of particles are entering from a thousand other sources,
including your own body, fine by me. It's your money. Like those
view windows, sounds impressive and it's a good selling point.
DOH!! Ya' got me!
I, who've worked with/around HEPA filters for years, couldn't possibly
know as much as you, who, with the irrefutable qualification of having
absolutely NO experience whatsoever with HEPA filters, disagrees with
my "opinion". I'm sure all ahr readers will gladly bow to your
overwhelmingly superior logic in this matter. Yeah, verily, Jim has
spoken. Go forth and buy HEPA!!
You seem to be confusing "HEPA filter" with "clean room". HEPA filters
are used in clean rooms, but they are also used elsewhere. The use of a
HEPA filter alone does not make the environment a "clean room", nor does
an environment which is not a "clean room" mean that the filter used
there is not a "HEPA filter".
....and Stanley Steemer Carpet Cleaners really do use real steam to clean
your carpet. Ionic filters work, too.
No, seriously, I am completely WRONG and you should all go out and buy
pallets of alleged HEPA filters for your house and your car and your
bird cage and ash tray and coffee maker and whatever the Hell else
they're making them for these days. Lords know you gotta capture
those microscopic pathogens no bigger than 0.00003" while clouds of
particles ten thousand times bigger are wafting through every window,
door, vent, hole, crack, etc in your house. Buy the really really
expensive ones. They work even better. Jinkies!
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