Air purifiers are wonderful and can definitely improve your quality of life. Unfortunately, a lot of the ones sold today can be hard to figure out.
You might find some labeled “true” HEPA filters while some others are advertised as “HEPA type.”
To make matters worse, as a new buyer it’s easy to be misled into buying a product that’s misrepresented and pretends to be as good as better-quality products.
In this post, I’ll explain the difference between HEPA type vs HEPA filters in great detail.
- True HEPA and HEPA type air purifiers
- HEPA-type vs. true HEPA explained
- Industry standard ratings
- HEPA-type marketing to watch out for
- Are HEPA type purifiers bad? Are there exceptions?
True HEPA and HEPA type air purifiers
Shown: 2 very common air purifiers, which don’t seem very different from the outside. Left: A Holmes HAP242-NUC air purifier which includes a HEPA-type filter and marketed similarly to a true HEPA filter. Right: GermGuardian AC4825 air purifier. It includes a genuine HEPA filter that meets the High-Efficiency Particulate Air (HEPA) standard.
The problem with air purifiers sold today (as pictured above, for example) is that it’s very easy to think they’re all the same. Because of clever marketing, you may think a HEPA-type is just as effective as a true HEPA product.
The problem lies in the details and how filters are rated.
What is a true HEPA filter?
A High-Efficiency Particulate Air (HEPA) filter describes a type of filter designed to meet efficiency and air purification quality levels set by the United States Department of Energy. These filters are made of a very dense fiber-like material.
To meet the standard a filter must be able to remove 99.97% of airborne particles that enter it down to 0.3 microns in size.
A filter’s efficiency refers to how many particles it can trap and remove from the airflow that passes through it. At 99.97%, for every 10,000 particles flowing into it only about 3 escape.
HEPA filters are very effective at cleaning the air!
The good news is that thanks to the High-Efficiency Particulate Air (HEPA) standard exist it’s much easier to know what you’re getting for your money.
HEPA-type vs. true HEPA explained
This graph shows how air filters like HEPA filters perform when used in an air purifier.
A HEPA filter’s efficiency actually begins to fall for particles near the size of 0.3uM, which is why they’re rated to “99.97% of particles down to 0.3uM.” Filters actually work even better above that size (as seen in the graph, like 5uM for example).
Following the red line on the graph, you can see that the efficiency (the number of particles it can capture) drops a bit near a certain size range.
The interesting thing to know is that filters actually trap more particles below that size range, but it’s misleading to sell a filter based on that.
Minimum particle size is what matters
The smallest particle size a filter can remove from the air is the most important thing to know. In the case of a genuine (true) HEPA filter, you can be sure that’s 0.3uM (less than 1 millionth of a meter).
“HEPA-type” filters are those that look like true HEPA filters but don’t meet the same requirements. They’re not standardized and can have any range of efficiency and minimum particle size rating.
HEPA-type purifiers are sold to give a buyer the impression they’re getting the same performance when in fact who knows? Unless the specs are specifically made clear, it’s anybody’s guess.
There’s no mandatory requirement for companies selling those to have proof of their product’s performance.
Industry standard ratings
An example Clean Air Delivery Rate (CADR) label from the Honeywell HPA160 medium-large room air purifier. CADR ratings are lab-verified cleaning efficiency ratings based on measuring how effective an air purifier is for 3 major types of air contaminants.
The industry standard Clean Air Delivery Rate (CADR) is a standardized test carried out by the Association of Home Appliance Manufacturers (AHAM).
The AHAM is an independent (non-government) voluntary industry association that was established to better rate and standardize the ratings of many appliances you buy.
Air purifiers have unique requirements as well so a method of testing their cleaning effectiveness was developed. Using the CADR you can better shop by comparison for those models which include the rating in their specifications.
Understanding CADR ratings
The CADR rating is a cleaning effectiveness rating. It’s a score based on standard lab tests by the AHAM where a purifier is used in a room with a measured amount of air contaminants.
The air purifier is then observed and measured based on how well and fast it can clean the 3 types of contaminants (smoke, dust, and pollen) in a given amount of time.
Air purifiers with a higher airflow rate (larger purifiers with more fan speed) will nearly always rate higher.
That’s expected. Therefore when shopping and reading CADR ratings you should compare purifiers of a similar recommended room size.
(For example, a small room purifier will have a lower CADR rating than a large room one, so comparing them as equals doesn’t make sense).
HEPA-type marketing to watch out for
You might find products advertised as having “99.9% efficiency” or something like that. But the most important thing is what’s the minimum particle size they can filter at that level? What is it? How does it really perform?
Unless it’s specifically made clear, you have no idea how well it’s actually going to work. More than likely it’s not close to the performance of a true HEPA filter and is a bad choice.
In some cases, HEPA-type filters can allow allergens, dust mite particles, and more to escape! That’s because some of the most common airborne particles that give people problems are smaller than they can capture.
Image showing the filters from the previously shown examples. A HEPA-type filter (Holmes air purifier, left) and a true HEPA filter (GermGuardian, right) look extremely similar. In most cases, you can’t tell the difference just by looking. You’ll need to be very careful and look for specifications that tell you their performance. However, in my opinion, “HEPA-type” filters are best avoided and you should simply get the real thing.
Avoid unknown HEPA-type filters. Don’t waste your money.
Are HEPA type purifiers bad? Are there exceptions?
As I mentioned earlier, it’s generally best to avoid HEPA-type purifiers. But there are exceptions to the rule.
The Holmes desktop air purifier I showed earlier is an example I can use. It’s more of a budget model. However, in this case, the manufacturer does specify it can trap contaminants down to 2 microns (2uM) in size.
HEPA type filters aren’t “bad” – just a different performance level
While that’s poor in comparison to a real HEPA filter, it’s still ok for some purposes. For example, for larger particles like dust mites, household dust, hair, and so forth it can work just fine.
In that case, you’ll need to be well-educated about what size particles your air problems include. I definitely wouldn’t recommend a HEPA-type filter for smoke, airborne microbes, and other issues. Smoke particles have been shown to measure well below 1 micron in size, for example.
Honestly, this kind of information isn’t for the average person and leaves too much room for making a bad buying decision in my opinion.