What is a HEPA Air Filter and Which is Best?

Hepa Air Filter

You might be wondering, “What is considered HEPA and what is ‘good enough’?”

I was recently asked that question regarding HEPA air filter for the home.

A HEPA air filter is one that will filter out very tiny particles and is particularly recommended for allergy sufferers.

I like HEPA because of the fact that less particulates enter the lungs while breathing!

How many of you have noticed this at one time or another in your home:

You’re sitting there and the sunlight is shining ‘just right’ through the window and you can see all that dust and particulate matter floating in the air! A moment later when the sun angle changes, you can’t even see it. But you know it’s still there!

A HEPA air filter will remove that stuff…


What does HEPA mean?

High Efficiency Particulate Air. It’s a standard for a type of air filter.

To qualify as HEPA by US government standards an air filter must remove (from the air that passes through) 99.97% of particles that have a size of 0.3 µm.

source: American Society of Mechanical Engineers (ASME AG-1a–2004)

0.3 µm, that’s really small!

1.0 µm is a micron, or micrometer. One millionth of a meter.

Particle Sizes:

0.2 – 3 μm : burning wood
1 – 5 μm : Anthrax
1 – 10 μm : Bacterium (typical)
0.7 – 90 μm : Asbestos
3 – 8 μm : Spider web silk strand
3 – 12 μm : Mold
10 – 100 : Human Sneeze
5 – 200 μm : Hair
70 – 180 μm : Paper thickness
100 – 300 μm : Dust Mites
10 – 1000 μm : Pollen

So imagine how small 0.3 µm is!


How Does HEPA Air Filter Work?

Keeping it simple:

A HEPA air filter is a mat of randomly arranged fibers. These fibers are typically made up of fiberglass and their diameters range between 0.5 and 2.0 micrometers.

Actually the air space between HEPA filter fibers is typically greater than 0.3 μm. However a HEPA filter acts like a sieve where particles become trapped as they stick to a fiber.


Are all HEPA air filters the same?

Short answer, no they’re not. Because some companies use marketing terms that may mislead.

Products that claim to be “HEPA-type”, “HEPA-like”, “HEPA-style” or “99% HEPA” may not or likely do not satisfy today’s HEPA requirements. They may not have been tested in independent laboratories.

Some of these filters may be sub-par quality while others might be reasonably close to HEPA filtration. Still others may fall significantly short, making them truly inferior.

Companies now have begun using a marketing term known as “True HEPA” to give consumers assurance that their air filters are indeed certified to meet the HEPA standard.

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 National Institute for Occupational Safety and Health N100 rating for respirator filters.


Which HEPA air filter is the best?

I would reason that the best HEPA air filter will be one that is rated “True HEPA”. Or one that has been tested and proven to meet the standard.

There are lots of different HEPA air filters that all meet the standard, so they’re all the best in that regard. From there it becomes a matter of features, form factor, design, fan speeds, quiet levels, price, etc.. which are fairly subjective.

There are tabletop filters, room size air filters, whole house air filters, and filters for all sorts of things including your furnace or even your vacuum cleaner.

I will say that I have the following ‘True HEPA’ room air filter and it has been great for us:

GermGuardian True HEPA

That said, I do have several ‘Rowenta’ brand fans and they have been the best and quietest I’ve ever owned. They also make a quality True HEPA air filter for larger spaces. I don’t own this, but it sure looks like a good one…

Rowenta True HEPA (800 sqare-feet)


HEPA Air Filter for preparedness

Besides the every day benefits of having one or two for your home’s air quality, a HEPA air filter is good for preparedness.

Why? I can think of two good reasons (at least).

1. Alpha Radiation
2. Pandemic Outbreak

Alpha Radiation Particles

A HEPA filter will assist to filter out alpha radiation particles. A nuclear ‘accident’ could conceivably release alpha radiation (not to be confused with beta, gamma, or x-ray radiation). Alpha is large and tends to cling with dust particles. All of which could be filtered into a HEPA air filter. It’s largely what’s inside a ‘fallout cloud’.

Pandemic Outbreak

While virus may likely be smaller than the ability of HEPA, a HEPA air filter will catch bacterium and/or cough & sneeze particulate which may contain the virus. If someone in the home is sick, this may help reduce the likelihood of others getting sick from breathing in ‘the cloud’.


  1. Please remember that all filtration devices will become the most contaminated object in your living area, when handling a used (even slightly used) filter please remember this.

  2. A ULPA filter with an electrostatic bar will capture 99.997 of particulate matter down to .12 microns. You want clean air, run that setup.

  3. Bought an IQAir Health Pro about fifteen years ago. It works great, but the filters are very pricey! The filters don’t require replacement at the same time (it lets you know individually on them) but a full set runs about $350.00. It has a pre-filter, a carbon filter for gases (like volatile fumes), and a HEPA filter last. It is very quiet, and the filters last quite a long time. Other than the filter cost, no complaints at all. On the other hand, the one suggested by Ken is probably a much better value!

      1. True! I’m one of the lucky ones that doesn’t have allergies, but have it more for the SHTF scenarios you mentioned. Your site is awesome, Ken!

  4. Wow, I’ve never thought of the benefits of an air filter. Thank you for the article, it was very informative.

  5. Vollara also offers a good line of products. OZone in not pollution, it’s O3, or activated oxygen. There’s been a lot of misunderstanding about that.

    1. One thing to keep in mind if you’re using a product that produces O3, ozone is the fact that it can affect some types of rubber goods, making them brittle. It is also very unhealthy for persons suffering from lung diseases and chronic breathing conditions. I know that because I am one of those people and on days when ground level ozone is high outdoor activity is exhausting. CR, I’m not sure what the company you’re referring to means by OZone but O3 is a pollutant when it is present at ground level. In the upper reaches of the atmosphere it not a problem. In fact there it protects the planet from UV radiation. In addition to natural rubber it also has a negative effect on mild steel and nitrile.

  6. Ken, thanks for this write-up! Early in 2017, I went to an Allergist and they confirmed my suspicions about having a few allergies. One of them is pet dander… and we have dogs.

    I’ve gotten to where I need to purchase an air system and will be giving your recommended HEPA filter a good hard look after the holiday! Our indoor dogs tend to stay in our den and when I’m in there, I begin coughing and my nose starts to run — typical symptoms of allergies. I think a HEPA filter will greatly reduce my symptoms.

    1. Modern Throwbsck, if you have pets, make sure you have hard surface floors and preferably leather furniture. The throw comforters can be laundered regularly, but the other stuff is really hard to clean. I had to do this because of pet allergies also. I also have allergies to outside things, and the pup seems to run through everything that doesn’t agree with me and then spread it around the house. By keeping her in he rooms with with hard surfaces which happen to be every room but bedrooms – huge difference.

    2. There’s no doubt that the HEPA filter linked above (or any that you find) will help. I have very mild allergies. Fortunately not bad like others…

      But when I turn on the air filter, it doesn’t take long and I notice a drastic improvement in breath-ability and ‘freshness’.

  7. When my mother was ill, I purchased for her a HEPA filtration unit at Wal-Mart. The unit has three filters along with three different filtration settings, General Cleaning, Germ, and Allergen. Energy Star rated. She was very allergic to airborne allergens, and this unit helped her a lot.

  8. Do an eBay search for nuclear grade HEPA filters. Several years ago got several brand new surplused ones from the shut down Rocky Mountain Flats project. Built a custom holder and prefilter for it. If you are going to spend the money get the best…surplus of course. These probably set the govt back about 700 a piece. Mine were 40-60 a piece. Flanders is the brand. They are over a foot thick, yet breathe well. Test to filter out the nuclear nasties as well as pollens. Get a activated charcoal filter (like they use on hemp farms) and you are NBC ready for your safe room or shelter. These charcoal canister type coconut carbon filters are the best…skip the thin flimsy cheepy ones. The canister type run from 30-80 dollars depending on air input pipe diameter. After all it is your life…have no regrets. God bless

    1. Bro James,
      You probably got them from the old Rocky Flats Nuclear Weapons Plant on the front range. ( now the Rocky Flats Environmental site ) They used to have a HEPA filter testing facility out there, many years ago. Most of the old HEPA filters you speak of had plywood frames back then. Do not know what they have these days. Please note that the HEPA filters must be protected from heat and flame by a non-combustible pre-filter. that HEPA filter media will burn if it gets hot enough or exposed to flames. just saying.

      1. And hopefully those nuclear filters haven’t already been ‘used’! Wouldn’t want to get one loaded with alpha radiation…

    2. Ken,
      Naw, everything sold as ‘excess’ out of Rocky Flats was surveyed before it was sold. Despite what you might have heard about Rocky Flats, they were very serious about controlling contamination. Very best of the best worked out there and in th he DOE weapons comlex.

  9. Good article Ken. Nice lead in to the sometimes complicated world of HEPA. For those folks that are looking for HEPA or ‘HEPA-like’ filters for their house HVAC (heating, ventilating, and air conditioning ) systems, you will find that the industry has been using a MERV (minimum efficiency reporting value) rating to apply to filters to give consumers an idea of what they are getting.

    A MERV of 1-13 is common in residential filters, and from 14-20 for industry and hospitals.( I believe that MERV ratings of 16-20 are in the HEPA range) Do a search on MERV ratings and you will get some pretty good recommendations.

    One thing to note is the volume of the stand alone filtering systems. While a stand alone filtering system may be highly efficient, if the air volume is low, it is not going to help much, IMHO.

    Using your home HVAC system with a less efficient filter will do a better job of removing the gross amount of pollutants from your air, but just not get the small stuff. That is unless you add an electrostatic air filter, or increase the blower power and add true HEPA filters.

    There is a lot of confusion still in the consumer part of the industry about HEPA filters and ratings that have to do with efficiency, but also air flow and pressure drop.

    The American Society of Heating, Ventilation, and Air conditioning Engineers (ASHRAE) has a new standard out to try and ‘level the playing field’ among the filter manufacturers so that consumers will benefit, ASHRAE Std 199-2016.

    1. Thanks for the referral to the ASHRAE standard. As is typical in many industries, you need a way to ‘level the playing field’ given all the marketing and misuse of terminology.

  10. Took an Asbestos abatement class at U of Wash, college of Engineering, way back.
    HEPA is high efficiency particulate absolute.
    Hepa filters are measured in microns nominal or absolute
    A nominal particle can be , say, 10 microns, in diameter, but long.
    An absolute particle can only be, say 10 microns, in all dimensions.
    A particle of talcum powder is 10 microns.
    Absolute filters are measured in microns absolute– much finer filtration, and will need more frequent change.

  11. Reading a lot of comments, it seems many have issues with allergies. Filters will help, HEPA filters for sure. But, for the best bang for your buck have an electrostatic filter installed in your HVAC system and run the fan all the time. An electrostatic filter can cost from t$450-800 + installation cost if you can’take do it yourself. It will remove allergens, smoke, even bacteria! And you clean it by washing every 6 months. With filters, one use and you gotta throw them all out. So when you ask “how good a filter do I need?”, I answer that with what I have, MERV 8 throw away filters for roughing, then an electrostatic filter to take the small stuff out.. just my thoughts fwtw, not gospel.

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