Are Air Purifiers A Waste Of Money?

Yeah, there’s a lot of talk about air purifiers and how they clean the air. But what’s the truth? Are they really as good as people say or are air purifiers a waste of money?

I’d love to clear this up once and for all for you. In this article you’ll learn:

  • The truth about what purifiers do (and don’t do).
  • The right and wrong kind of purifiers to buy.
  • Do air purifiers cause any side effects?
  • How are air purifiers rated?

Do air purifiers really do anything?

diagram showing air quality problems air purifiers can help with

Air purifiers help with a range of very common air quality problems that can affect your comfort and even your health. In fact, the right kind of air purifier doesn’t cost a ton of money and for many people is a great investment.

Do air purifiers really work?

The simple fact is that yes, high-efficiency particulate air (HEPA) type air purifiers do effectively clean the air and make a helpful difference for a good number of air quality problems. However, not all products sold as air purifiers do much of anything. I’ll explain exactly what I mean in this article.

It’s very important to understand a few things that can make a huge difference:

  • There’s a big difference in quality as some air purifiers aren’t as good as others (don’t clean the air as effectively).
  • You should always use a purifier that’s correctly matched to the room size you’re using it in. (I’ll go into more detail about this later)
  • Clean air delivery rate (CADR) air purifiers give you lab-proven cleaning performance numbers to help you pick a better quality product. I’ll explain this later as well.
  • Some products that are not HEPA-type purifiers, sold as air purifiers, are not effective and don’t do much.

A good air purifier can trap a wide range of airborne contaminants that affect your comfort & even your health:

  • Allergens such as those from pets (pet dander), dust mites, plants, and more.
  • Household dust and fibrous particles from carpet, building materials, and what you bring inside from the outdoors.
  • Viruses & microorganisms that can make you sick.
  • Some airborne aerosol substances and other airborne chemical compounds.

What is a HEPA filter?

High-efficiency particulate air (HEPA) filters are high-performance air filters using a compact & folded design made up of very dense, randomly arranged fibers (made of polypropylene or fiberglass). They’re fixed permanently inside a rigid frame around all four sides that supports the filter material and makes installation & removal simple.

It’s basically an extremely dense filter that traps microscopic particles (down to about 0.3 microns, or millionths of a meter) as they move into the fibers as a purifier circulates the air. HEPA filters permanently capture airborne particles meaning they have to be replaced once they’re very dirty.

The HEPA name reflects a long-standing air filtration standard set many years ago by the United States Department of Energy and has been a commercial standard since the 1950s. The standard requires that 99.97% of all particles down to 0.3 microns in size be trapped as they pass through the filter.


HEPA filters are commonly used along with a pre-filter section that traps the largest air particles like dust and hair before they reach the main filter. Pre-filters may also include an odor absorption activated carbon coating which HEPA filters don’t offer.

You can often vacuum a pre-filter to prolong its life and help keep the purifier running efficiently (by preventing the airflow from becoming poor due to too much blockage).

How long do HEPA filters last?

The typical life expectancy of a HEPA filter is about 6 to 8 months or so, depending on the size and how bad your air quality is.

Are air purifiers worth the money? Which ones are bad?

are air purifiers worth the money section image

Yes, a good air purifier is well worth the money you’ll spend. The good news is that HEPA purifiers are actually a good buy and you don’t need to spend a ton of money to enjoy clean air.

You’ll pay on average around $80-$100 for a good model for medium-sized rooms, for example. Of course, some offer even better performance and features (like smartphone control) but it’s not critical. The main thing to know to look for is:

  • A well-reviewed brand or model. This tends to be mainly from brand name manufacturers.
  • Models using a true HEPA filter – not “HEPA type.” HEPA-type purifiers don’t meet the same filtration standard.
  • Purifiers with the recommended room size provided. This will help you pick the right one based on the room where you’ll be using it. This is most often listed in square feet (room length x width, in feet).

Purifiers to avoid

Ionizer and ozone generator examples image

Left: an ionizer sold as an air purifier. Right: an ozone generator.

Ionizers and ozone generators are very similar in how they work but generally speaking ionizers produce charged atoms in the air to attract airborne particles to a metal plate or a similar object like a filter.

They typically don’t introduce a high level of emissions into the air, so they’re generally safe and not that likely to cause discomfort such as headaches for example. Additionally, ionizers are proven (under the right conditions) to reduce sickness by reducing the number of airborne sickness-causing microbes.

The problem is that they’re not very effective for the most common household air quality problems. They simply don’t work anywhere near the effectiveness and efficiency of a HEPA purifier.

The problem with ozone generators

Diagram showing ozone production and pair particles

Ozone generators work by producing large amounts of O3 molecules (ozone) by splitting oxygen molecules (O2) from the surrounding air. Some of these recombine to form ozone with a charge that attaches them to particles in the air. At low 

The truth is, ozone generators don’t purify the air without health risks – or as effectively – as filter-based products do.

While it’s true that they can trap some elements in the air like dust, pet dander, and similar particulates, they’re not efficient at doing so. The reason is that when ozone (O3) molecules are produced, they have a short life span before recombining back into oxygen molecules at some point.

An ozone generator, generally speaking, produces a lot of ozone in a room. The idea is that by doing so allergens and other contaminants will bond with the ozone causing it to fall to the ground or be trapped in a filter if provided.

The main problem with this is that it takes a significant amount of ozone to make a worthwhile difference – so much so that it’s bothersome or even harmful to be in a room with very high ozone levels.

What are the side effects of air purifier use?

Image of child in living room with air purifier

Regular filter-type (HEPA) air purifiers have no side effects at all. This is because unlike other types they don’t add anything to the air around you. They simply circulate the air in the room and remove particles as they pass through the filter.

The end result is blowing out clean, healthy air. Some models (not many) also include a feature such as “PlasmaWave” or some other type of ionizer as a very small secondary way to clean airborne elements. However, typically the amount of ions produced is very small & pretty much not enough that you’ll even notice.

It’s extremely rare to have a HEPA purifier that generates ozone – those types basically don’t exist.

Ionizers and ozone generators, however, (mainly ozone generators) can cause some side effects:

  • Headaches
  • Respiratory irritation and discomfort in breathing
  • Dry eyes
  • Allergy-like symptoms due to the molecules present in high levels that they’re inhaling or in contact with the skin

In fact, I’ve had a few readers contact me regarding ionizer products sold as “air purifiers” installed in their home’s HVAC system. Those can produce very high amounts of ions that cause the side effects I listed above.

You’ll never have that problem with a regular filter purifier.

How are air purifiers rated? What is the Clean Air Delivery Rate?

Example CADR rating label with notes explained

The Clean Air Delivery Rate (CADR) is an industry-standard rating, based on testing in a lab, that describes an air purifier’s air cleaning effectiveness for particles from 0.10 to 11 microns in size.

While not mandatory in the industry, it’s often used by better air purifier manufacturers to provide buyers with a way to choose the best air purifier based on proven numbers instead of advertising claims. The higher the CADR rating, the faster the unit can clean your air.

Basically, the idea behind it is that manufacturers use an independent test company to verify the performance of their products. If the claimed air cleaning performance isn’t met, they’re not allowed to display the certification label on the product box.

Long story short, this all means that the CADR rating will help you pick an air purifier that’s right for the room you use it in, your air quality problem, and you can buy with confidence based on a reliable & proven standard.

What is the cubic feet per minute (CFM) rating for purifiers?

With or without CADR ratings, purifiers are often rated for their airflow rate (how much air they can move) which is expressed in cubic feet per minute (CFM) in the United States and a few other countries. (This is listed sometimes also in cubic meters per minute.)

Purifiers with a higher CFM rating can move air more quickly for cleaning and normally are more efficient at cleaning a room’s air (and usually have a good CADR rating, if available). The CFM rate will depend on the size of the purifier as smaller models have smaller fans that can’t move the same amount of air as quickly as larger models.

Do all purifiers sold have a CADR rating?

Do all air purifiers have a CADR rating

No, CADR ratings are not provided for all air purifiers sold. Only for those that the manufacturer has submitted the product to the Association of Home Appliance Manufacturers for testing and that have passed the test requirements.

That’s usually well-known, larger manufacturers such as Levoit, Honeywell, Winix, GermGuardian, and some others. It’s rare to find “off-brand” air purifiers with CADR ratings listed. If they’re not provided by the AHAM, then they may not be legitimate at all.

What are the disadvantages of air purifier use?

what are the disadvantages of air purifier use

Really there’s not much, if anything, to be concerned about when it comes to air purifiers and any disadvantages you may be worried about. But there are a few minor things to know:

  • You’ll need to factor in the cost of maintenance (replacement filters). This is usually fairly low (say $15, $25, or $35 for original quality filters) but some models can be more expensive. It’s smart to check before buying a particular model.
  • They only use a slight amount of electricity (close to what a fan uses: about 15W, 25W, or 55W depending on the fan speed setting) so they won’t hurt your electric bill much at all.
  • Ideally you’ll want to leave your purifier running for most of the day or even 24/7. That’s because once the air is initially cleaned, keeping your purifier running maintains the cleanliness of the air without letting the air quality level reach its original bad level.
  • Purifiers cannot remove mold completely – only airborne spores. Mold has to be removed directly at its source otherwise it will continue to present a health problem.

Additionally, it’s worth considering that purifiers need a little bit of space between themselves and a wall or furniture – typically about 1-2 feet or so to allow proper unrestricted airflow.

If you’d like a model that has a self-off timer or you can control while away, you’ll need to shop for a model that offers those features. Basic air purifiers of good quality work well but you won’t be able to shut them off while you’re gone.

Do doctors recommend air purifiers?

do doctors recommend air purifiers image

Yes, some doctors recommend air purifiers to people with allergies, respiratory problems, and other health issues. Unfortunately, not enough doctors offer air purifiers as a possible alternative to some problems as opposed to prescription medication or other treatments.

Grant Williams

About the author

Grant is a professional engineer by trade and has experience with both maintenance and do-it-yourself home projects. He enjoys sharing his expertise & ideas with others to help them improve their comfort and quality of life. Read more »

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