HEPA Air Filters and Why You Need One
A Buyer's Guide

July 2013

Earlier I talked about cleaning vinyl LP's.  I also mentioned a bit more about the dust problem in Part Two of the vinyl cleaning article.

Dust is a nuisance for any kind of electronics.  It's also not very good for your health.  

In 2013 it's hard to get away from air pollution.  Modern civilization has a lot of ways to foul up the air.  Even livestock farming has been transformed into an industrial operation... complete with super-sized odors and health hazards.

Even if you don't live next to I-5 in Los Angeles or an industrial pig farm in Middle America, there are enough nasty things in nature that you can really benefit from a HEPA filter.  I don't have an SEM handy to show you the horrible creatures, but I did look at some household dust under a light microscope, and I found a hideous lobster-claw thing that still has me guessing to this day.  Whatever that claw was once attached to, I wouldn't want to meet it.  (SEM stands for Scanning Electron Microscope, but you probably knew that already.) 

Household dust is gross.  It contains living things.  It contains non-living but very gross things.  It contains pollen, mold spores, mites, paper fibers, cat dander, stray bits of fiberglass insulation, and various other things you might not want in your lungs.  Once you breathe these things in, some of them never go back out.  

What you're seeing here is a layer of dust about 1/4 inch thick.  Someone never bothered to vacuum their pre-filter (nope it wasn't me or the Mrs.).  A heavy dust layer puts strain on the motor, meaning it can go bad.   Keep your pre-filter clean.

Tiny Particles Filtered

True HEPA units can remove particles down to about 0.3 microns, which means they're trapping a lot of the troublesome auto exhaust soot that you might have read about.   The dangerous size range for these is up to about 2.5 microns, which is plenty big enough to get stuck in a HEPA filter.  There are also "hyper-HEPA" units that go down to 0.003 microns.  We'll talk about these shortly, and yes, they're awesome.


Dust mites are pretty nasty looking under a scanning electron microscope.  They also cause allergic reactions in millions of people.  Ever had what seems like a chronic, low-grade cold?  Couldn't stop sniffling and sneezing, even in winter?  For a lot of people, dust mites are the cause of all this trouble.  HEPA filters will take these little beasts out of the air.  They will also remove most kinds of bacteria.

Hyper-HEPA will remove viruses too!

Cameras, Music, & Electronics

Now we get to the original reason why I wrote a HEPA filter article for a camera-related site. 

We've already talked about dust as it relates to cleaning vinyl LP's.  Another huge benefit of clean air is that you're less likely to get dust on your DSLR sensor.  Once it sticks there, it will often stay on the sensor even after repeated attempts to remove it.   Dust specks may look small on the sensor, but they make big blotches in the pictures.

This is a photography-oriented site, primarily, so I should really emphasize the importance of HEPA filters if you're into cameras.  I have gotten dust on a DSLR sensor, and it has defied all attempts to remove it. 

Film cameras can tolerate dust somewhat more readily (since the "sensor" is replaced every time you advance the film), but dust contributes to wear.   The place where you load your film into the camera should be relatively free of dust.  This is especially true with 4x5.  Some people like to load their film sheets in a bathroom, first running the hot shower for a while so the steam takes the dust out of the air.  (And don't forget to turn off the lights before opening the box of film....)  You can do that, but not everyone has a hot shower in their darkroom.  A HEPA filter in your film loading area is really, really helpful.  (Before you even run the filter, first vacuum all the excess dust out of the place.)

What to Look For In An Air Purifier

First, I have to mention that those "ionizer" units are a mixed bag, and I lean heavily toward not using them at all.  The reason I steer clear of them is the ozone they generate.  Some people say great things about these units, but the problem is that ozone is toxic.  It is also a sensitizer.  Even if you don't have breathing problems now, you will eventually have them if you keep breathing ozone.  I ditched my "ionic air cleaner" and got a HEPA filter.  The HEPA filtration unit has proven to be so much better that there's not even a comparison. 

Some HEPA units have ionizer capabilities, but usually you can turn this feature off.  I would.

To me, here are the biggest considerations in choosing a purifier:

1 - Is it true HEPA?   True HEPA means it can filter 99.97% of particles down to 0.3 microns.

2 - How big a room can it clean?  Look at the CADR, which we'll discuss shortly.

3 - Does it have an outer dust filter that can be vacuum cleaned?  This is a huge plus.

Noise is another consideration, but if you're not living in the same room with the filter, maybe it's not as much an issue.   Most of the name-brand units on the market are pretty quiet on "low" and reasonably quiet on "medium".  Turning any of them up to "high" will result in noise.  If you don't mind the sound of rushing air, maybe it won't bother you.

The better units have at least three filtration stages:

1.  Pre-filter
2.  Carbon filter
3.  HEPA filter

The pre-filter will trap a lot of the bigger dust particles and of course hair.  The more dust accumulates on there, the more easily it will trap dust.  After a while, though, this puts some real drag on the motor and can even wear it out prematurely.  I wouldn't take the chance, because there's always a possibility it could burn up the unit.  Make sure you periodically vacuum-clean the pre-filter.  

The carbon filter mainly traps odors. 

The HEPA filter is what traps the really small particles such as auto soot, mold spores, and that sort of thing.

I said before that room size is a major consideration.  Here's the usual way to figure out what size filtration unit to get.  First, measure your room square footage.  This is simply the length times the width of the room, in feet.   A 20 by 10-foot room would be 200 square feet. 

Next, take that number and divide it by 1.5.  This gives you the suggested CADR, which stands for Clean Air Delivery Rate.  This is a standard rating for air purifiers.  A 200 square foot room would require a CADR of about 133. 

If you're already looking at CADR numbers, simply take the CADR and multiply it by 1.5 to get the number of square feet it can handle.  The Whirlpool AP51030K, a very good unit for the money (through this link), has a CADR of 315.  Thus, it could handle 472 square feet with no problem at all. 

Just know that the CADR conversion is not a strict cutoff, but don't push it too far.  A unit rated for 472 square feet could handle a 500-square-foot room pretty easily, but if you're looking at 600 or 800 square feet, get a bigger machine.   You can use a purifier in a bigger area than it was intended for, but it just won't clean the air as fast or as well.   What will happen is that it may not take stuff out of the air fast enough if there is something that generates allergy-causing particles (such as a cat...)  You'll end up having to turn up the unit to a higher setting.  It's a good idea to stick with the CADR ratings or very close to them. 

Some manufacturers don't like to use CADR.  This is debatable, and we're not going to spend pages and pages detailing it, because in the end it doesn't really matter as much as anyone says it does.  If the maker offers a CADR number, at least you know how to use it, and if they don't, they'll tell you how many square feet they recommend.  No problem either way.  The only time you would have a problem is if it's a cheesy, no-name manufacturer who is being shady.  Then you'd want to look into it a little more.  There are a couple big makers that don't use CADR, and their products are still reputable.  Maybe more so.  The one thing you should know, if you can't get a CADR, is how many air exchanges per hour the machine does.   I think the allergy associations say that number should be six.  My experience is that if a unit will do four, it's usable.  The air exchanges per hour depends on the size of the room. 

Some Choices

Here are some air purifiers with good features.  Like most other things, the ultra-cheap ones are never as good, so I'd really skip the $40 units if I were you.  Circa 2013, it seems like the tolerably good HEPA units start in the $175 to $200 range, they get a little more tolerable at $250 to $400... and $600 to $900 is where I'd be looking if you're getting serious about clean air.   

The $40 units will remove airborne cats from the air, the $200 units will remove cat hairs, the $600 units will remove cat dander...

(That was a joke.  They'll all remove cat hairs and cat dander from the air.  The question is how well... and what else can they remove that's smaller.)

First, the tolerably good choices if you're on a budget:


The Winix air purifiers have PlasmaWave technology, and some people have complained about being sensitive to it.  The 5500 and the 9500 both allow you to turn it off if it bothers you.   I prefer a purifier that doesn't throw a bunch of "ion" stuff on top of the basic HEPA technology, but I don't mind a unit where you can at least disable the add-ons.

Next up, the upper-mid to high-quality range.   The one I wanted to like the most was the IQAir New Edition HealthPro Plus, currently $899 through this link.  Just know there could be an issue with the gas & odor filter it uses.  These "V5 Cell" filters have been known to emit a nasty odor that makes it worse than having no air purifier at all.  Not all of them do it, though.  A lot of people have been using the V5 filter with no trouble.  Or, you can just run the purifier without the V5 filters.

Better yet, just get the IQAir New Edition HealthPro (not the Plus) or the HealthPro Compact.  These don't come with V5 filters, so no weird odor problem.  If you hear people complaining about the weird smell with these models, they're actually talking about the Plus model, or else they fitted a regular HealthPro with a V5.  Once again, the regular HealthPro and the Compact do not come with V5 filters.   The HealthPro has a space for a V5 if you really want it, but it doesn't come with it.  The Compact does not have a space for the V5 at all.  Both units are rated for 1,240 square feet.  Basically you'd be paying $50 more for that space to put a V5.  Worth it?  You decide.  Even hyper-HEPA can't filter gases out of the air, so if you live in a place where odors are a problem, you'd need something like this.  Maybe they'll figure out the odor problem with the V5, and if they do, you'll have the place for it.


Finally, we get to the top of the line:  the IQAir Cleanroom H13.  At nearly two grand (available here at the time of this writing), this is a serious air purifier, but you can know you're getting serious quality.   This purifier is no joke. 

The first thing you should know about the H13 "Cleanroom" unit is that it doesn't cover as many square feet as its more affordable brethren.  It's rated for 625 square feet.  Whoah, wait a second:  it's twice the price, and it covers half as many square feet?  625 is still a pretty good number, but what's the deal here?

Well, "Cleanroom" is a pretty bold term.  If you're not a tech person, this term might not really mean anything to you, but cleanroom implies a pretty high standard of air cleanliness.  Cleanrooms are where they grow semiconductor crystals, build NASA contraptions to fly to Mars, and all that other stuff where you don't want any particles messing stuff up.

The other IQAir units have hyper-HEPA (0.003 micron), but the Cleanroom H13 is a hospital-grade purifier.  They really put a lot of emphasis on "antimicrobial" here.  This unit doesn't just trap germs... it kills them.  That's actually a pretty big deal, because other filters once they get clogged can start to re-leak germs back into the room.   The idea with the H13 is to take them out permanently.   Could you imagine in a hospital with a regular HEPA filter... "Oh by the way Charlie, you might want to wear a biohazard suit when changing the filter... we had a TB outbreak last week."  I don't see that happening with the H13. Just my opinion, though.

The Cleanroom H13 is good enough for tuberculosis wards and pretty much anything else of that sort. 

If your hobby is grinding NASA-grade telescope mirrors, I'm sure it will work for that, too. 

If this purifier fits your budget, get one and know what it's like to have really clean air.   Since you breathe air more often than you drink water or eat food, it could be a wise investment in your health. 

For some people, an air purifier could mean the difference between breathing, and not being around anymore.  People with breathing problems such as asthma or COPD can be very sensitive to anything at all that's floating around in the air.   When you're talking about something that important, it doesn't make sense to skimp.   (Disclaimer:  This is not medical advice.)

Parting Thoughts

I really suggest getting a HEPA air purifier, no matter where you live.  Your health is worth it.  Even if you think you don't have enough money, skip the restaurants a few times and you will have enough for a passably good purifier.  Ten, twenty, thirty bucks each time at a restaurant adds up quickly...  a person could accumulate $175 to $200 for a purifier in no time.  One thing that amazes me is that a lot of people would rather take the chance of debilitating health problems later in life.  You're smarter than that, which is why you're reading my website :-)

My overall top choice would probably be the regular HealthPro purifier (currently $849 here).   You can save a little bit by not getting a stock V5 filter, but you can always buy one later if you really want to try it.  The germs not being destroyed is not such a big concern if they're only your germs.  In a hospital, it's sort of a different situation.  

The H13 is a good choice, though, if someone could be bringing germs into your home from somewhere else.  Many bacterial and viral diseases are transmitted in the air.  If you could take some of these out of your air, it might be helpful. 

Anyway, the point is that a good purifier is totally worth it.  I don't know that it would protect you from Ebola, but there is something of which I'm fairly sure.  Once you try a good HEPA unit for a while, you won't want to be without it. 

UPDATE:  If you invest in a purifier, I highly recommend a real surge protector so your purifier will last a long time.

I hope you liked this article.  Please help me keep this site on-line by purchasing your stuff (pretty much anything) through the links on this site.

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