HEPA Air return filters

Hi,
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 purchase them?
Thanks!
Sam

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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.

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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 isn’t 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 doesn’t freeze then you’re ok.

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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.

ransley full-quoted:
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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.

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$imple $olution co$t money

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Thats a good idea, it would increase winter efficency and save the coil from being crapped up, its just more $ so few think about it

ransley wrote:
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Where do you buy those filters? I have an ideal spot to install one, and have been thinking about just that.

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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 sites.

Sam Takoy wrote:
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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.

"Sam Takoy" wrote in message
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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... HVAC HEPA or Mechanical contractor HVAC
Also you can get stand alone HEPA air cleaners at Walmart.

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Mine is not hepa and is 4" its an April Air, a Hepa would likely be 12-14" thick and cost a bundle to maintain.

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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 nonsense.
nb

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You do seem to relish being *boldly* ignorant--
Just to keep it easy- here's a copy/paste from Wikipedia- -start wiki-quote- "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." -end wiki-quote-
I'll grant you that Wikipedia is a pretty shake source-- so I welcome anything other than your opinion on the matter.
Jim
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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.
nb

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My dogs shake off more particles than a Hepa room would allow

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none-- But I don't need to work in a clean room to know that HEPA filters are used in other places.
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He isn't looking for a HEPA certified house. He is looking for a HEPA filter.
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So far all I've seen is your opinion. What is there in IEST RP-CC001.5 that the furnace filters sold as HEPA filters don't comply with?
Jim

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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!!
nb

notbob wrote:
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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".

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....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!
nb