Essential Air Purifier and Air Cleaner Info

How a HEPA air filter works

Essential Air Purifier and Air Cleaner Info

Do you really need an air purifier also known as an air cleaner?

Air purifiers are most useful for people who suffer from allergies, asthma or other respiratory illnesses. They can also be helpful if you live or work in an environment with unhealthy levels of dust or pollution.

I remember my final year of post-graduate studies when the college campus shifted close to an industrial zone. The effects were clearly observable in many of my school mates and faculty. We experienced a significant increase in eye soreness, sneezing, sore throats and coughing. My favorite professor, whom I had known for 6 years, developed a permanent running nose and cough at the new location.

And these effects were on regular people with no history of allergies or other respiratory conditions.

It’s one of the reasons why I know that air quality does affect our quality of life and long term health. That’s where air purifiers come in.

The Importance of Choosing the Best Air Purifiers

A good quality air purifier can effectively filter and clean the air at home or in the office. It helps improve air quality and reduces the harmful effects of pollution. Conversely, using a poor performance air purifier can do more harm than good as it lulls us into a false sense of safety.

Key Features in the Best Air Purifiers

You’ll often see air purifiers that state they are 3 stage or 4 stage filters. These refer to several filtering stages. The most common are:

  1. Pre-filter

  2. HEPA filter - this is the main filter

  3. Odor filter - typically a carbon filter

  4. Ionizer, ozone generator or something similar

  5. Germ, bacteria and virus killer - usually using UV light or chemicals

While there are many possible features, the best air purifiers need to have some essential ones.

Essential features:

  • True HEPA filter

  • Pre-filter

  • AHAM VERIFIDE for room capacity and Clean Air Delivery Rate (CADR) for dust, pollen and tobacco smoke.

  • Timer

Other optional features:

  • Odor Reduction

  • Ionizer

  • Ozone Generator

  • Air Quality Sensor

  • Automatic Speed Control

Let’s find out what each of these features are.

HEPA Filter

HEPA filters are considered the industry standard for effective air filtration. This is the key core component in all air purifiers.

HEPA filters for air purifiers - The Wiser Buyer

HEPA filters come in a variety of shapes and sizes.

Did you know? HEPA filters were originally developed during the Manhattan Project (the folks who built the first atomic bomb) to filter radioactive particles for the nuclear industry!

HEPA is short for high-efficiency particulate air. A HEPA filter is a fairly simple mechanical filter. How it works is pretty easy to understand. Air is forced through the high-efficiency filter, which is a fine mesh. Particles such as dust, pollen, tobacco smoke and other small particle pollutants are trapped by the fine mesh. This results in filtered or cleaned air passing out on the other side.

What’s important to note is: Not every HEPA filter or HEPA air purifier is made equal.

There are numerous cheap air purifier models that are “HEPA type” or “HEPA like”. However these purifiers do NOT use a True HEPA filter. An uninformed consumer might know that they should get a HEPA purifier, but be easily confused into thinking that they are buying a cheap non-HEPA model that has a lower grade HEPA-type filter instead of a true HEPA.

What’s the difference between a True HEPA filter and a HEPA pretender?

A True HEPA is a particle filter that meets the standard of the US National Institute for Occupational Safety and Health (NIOSH), which states that “All HEPA filters should remove at least 99.97% of airborne particles that are 0.3 microns in diameter.”

For some visual perspective, 1 micron is 1/25,000 of an inch and human hair ranges from 50 to 150 microns in thickness. Try to picture 0.3 microns. It’s pretty small!

HEPA filter-how small is 0.3 microns

A HEPA filter traps 99.97% of 0.3 micron sized particles.

At that efficiency, a True HEPA filter is able to stop dust, pet dander, dust mites, pollen, plant spores, fungi, mold and bacteria. This makes HEPA filters effective in aiding people with asthma or with allergies to pollen, dust, etc.

A HEPA type or HEPA like filter does not have to meet any standard of performance. The main similarity is that they look like a true HEPA filter. They might claim to be 99.97% efficient, but that could be for large particles such as your hair! Such an “air purifier” would do little to filter out fine dust, pollen and other small particles that a true HEPA would easily trap. And is the whole point of getting an air purifier in the first place!

HEPA filters do need to be replaced once they are clogged which could range from 3 months to a couple of years depending on frequency of use and the environment.

So the most important thing is to make sure any air purifier you buy has a True HEPA filter.

There is an even higher performance type of filter called a Hyper HEPA. A Hyper HEPA filters even smaller, ultra fine particles as small as 0.003, which is 100 times smaller than the 0.3 micron rating of a True HEPA. These types of filters are used in air purifiers for hospitals and clean rooms such as research labs. If your circumstance requires such high performance, the good news is there is a consumer air purifier with a Hyper HEPA filter - the IQAir HealthPro Plus.


Most high quality air purifiers have a pre-filter. You’ve probably seen a pre-filter, which is a simple mesh commonly found in air-conditioners.

pre-filter for air cleaner air purifier

A Pre-filter traps large particles.

The function of a pre-filter is to trap large particles such as hair, fur, and clumps of dust and dirt before they reach the HEPA filter. This is very important because without a pre-filter, these large particles would quickly clog the HEPA filter.

A clogged HEPA would need to be prematurely replaced, which can be quite costly in the long run. On the other hand, a pre-filter typically is a permanent reusable filter that can be vacuumed or washed.

We do not appreciate manufacturers of a few expensive brands that choose to not include a pre-filter in their air purifier designs. In our opinion they are just trying to milk customers by forcing them to constantly buy expensive proprietary replacement HEPA filters. Something that can be prevented by including a relatively cheap and simple pre-filter.


AHAM verified home appliance

AHAM Verifide Mark

The Association of Home Appliance Manufacturers (AHAM) is an organisation that has been testing home appliances in independent third party laboratories in order to verify their performance since 1967.

We always like to see products that are AHAM VERIFIDE, as it provides assurance of their stated performance claims compared to unverified manufacturer claims that might be inflated.

The AHAM VERIFIDE program is voluntary and when a manufacturer signs up for it, AHAM randomly picks their products and tests them to ensure they meet the manufacturer’s stated specifications. Products that fail are not allowed to bear the AHAM VERFIDE mark.

Air Purifiers (and other appliances) that have been tested bear the AHAM VERIFIDE mark on a label that provides verified performance data. For air purifiers, the tested ratings include suggested room capacity and CADR for dust, pollen and tobacco smoke, which is explain below.

CADR and Room Capacity

AHAM VERIFIDE air cleaners are tested to ensure they perform according to manufacturer’s specifications for Room Capacity and Clean Air Delivery Rate (CADR). In addition, AHAM is authorized by the US Environmental Protection Agency (EPA) to test for the ENERGY STAR® certification program.

CADR is a measure of the volume of filtered air an air cleaner can deliver in cubic feet per minute. The higher the rating, the faster the unit filters the air. AHAM VERIFIDE air purifiers are tested for the three pollutants - tobacco smoke, pollen and dust, with ratings for each. See more at AHAM’s webiste.

AHAM VERIFIDE Air Purifier CADR-Energy-Label

AHAM VERIFIDE Air Purifier Labels show Suggested Room Size and CADR for Tobacco Smoke, Dust, and Pollen.

Room Capacity is then derived based on CADR ratings. While AHAM provides suggested room capacity, the figure is based on operating the unit at maximum power. For long term real-world use, we recommend using a unit that has up to 50% more room capacity than the actual room size measured in square feet. This will allow the air to be purified efficiently and effectively with the unit run at low or medium settings. This can help save energy and possibly extend the life of the unit. An added bonus is quieter operation as any unit run at maximum speed will be many times noisier compared to running it at low speed.

Another simple way to estimate room capacity is to use CADR as an indication. An average CADR (smoke, dust and pollen) of 200 is ideal for a 200 square foot room with a limit of 300 square feet. That’s a 1:1 (ideal) to 1:1.5 (stretching it) CADR to Room Size ratio.


This is a simple function that’s a toss up between being essential or optional. It can be a useful feature to let the unit clean the air without having to worry about forgetting to turn it off. A typical scenario could be setting it on a 6 or 8 hour timer while you sleep. We’ll say it’s essential in the interest of saving energy by not having a unit run 24/7.

Optional Features:

Odor Reduction

This could be essential for some while completely irrelevant for others. This is usually achieved with the use of an additional carbon or activated charcoal filter. Some designs might incorporate this into the pre-filter or the HEPA filter.

Ionizer and Ozone Generator

An Ionizer or ozone generator is used in some air purifiers. They do not filter air, instead an ionizer produces negative ions that attach to particles in the air. This makes them cling to surfaces instead of floating around. The impurities are not actually removed by a filter, they just attach themselves to various surfaces. This could include your lungs and respiratory tract!

Some studies have shown that these charged particles are potent irritants that can cause lung damage.

Ozone is another dangerous substance produced by ionizers and ozone generators. Ozone is 3 bonded oxygen molecules (O3). Exposure to high levels of Ozone is associated with lung disease and is especially dangerous for people with asthma, chronic lung disease or weaker constitutions such as young children and the elderly.

For these reasons we do not like ionizers and ozone generators. In our opinion the potential risks outweigh the benefits.

Air Quality Sensor and Automatic Speed Control

These two features usually come hand in hand. An air purifier with an air quality sensor measures the pollutant level in the surrounding air and then automatically adjusts the fan speed according to the level of pollution.

Most units with these features also have some sort of indicator light which shows the level of pollution - green for clean air and red for polluted air or something along those lines.

While the fancy light show feature is a non-essential visual feature, we do like the automatic operation and think it can be useful. However units with these functions typically command a premium price and you could probably save a hundred dollars on a unit that cleans just as effectively without the bells and whistles.

Best Air Purifier Brands

Honeywell Air Purifier

Honeywell is probably the best known air purifier brand in the USA. It’s also the #1 brand that is most recommended by allergists.

Honeywell makes air purifiers that are generally no-frills workhorses that get the job done effectively and provide years of reliable service at very reasonable prices.

Three of their popular models that easily make it into our top 10 picks are the:

  1. Honeywell HPA300 - great for extra large rooms (AHAM certified for rooms up to 465 square feet) and comes in black, which provides a color alternative to Honeywell’s typically functional looking white designs.

  2. Honeywell 50250 - AHAM certified for large rooms up to 390 square feet and costs a good bit of change less than the HPA300 model above.

  3. Honeywell 17000-S QuietCare - Designed for quieter operation, this model is especially suited for bedrooms and smaller rooms (AHAM certified for rooms up to 200 square feet).

All three models are available with Prime shipping and going for less on Amazon than the Honeywell store.

Honeywell 50250

Buy Honeywell 50250 Air Purifier

For Large Room:

390 square feet


  • True HEPA
  • Carbon pre-filter

Honeywell HPA300

Click to by Honeywell air purifier for large rooms HPA300

For X-Large Room:

465 square feet


  • True HEPA
  • Carbon pre-filter

Honeywell 17000-S

Buy Honeywell-17000-S-QuietCare-Permanent-True-HEPA-Air-Purifier

For BedRoom:

200 square feet


  • True HEPA
  • Carbon pre-filter

IQAir ProHealth Plus Air Purifier

IQAir might not be a household name like Honeywell, but they are considered the best air purifiers in Europe, where standards of quality are usually much higher. And higher quality is indeed the case with the IQAir HealthPro Plus Air Purifier. In fact it is in a totally different class from everything else.

Some of the outstanding features:

  • Hyper HEPA - this is the grade of air filter used in hospitals and outperforms true HEPA filters by 100x - literally. While a True HEPA filter traps 0.3 micron particles, a Hyper HEPA traps 0.003 micron particles.

  • 900 square foot room capacity! The IQAir has the most powerful fan of any consumer air purifier. And despite that much power, it’s pretty quiet, thanks to the well sealed design that also maximizes filter efficiency.

Winix Air Purifiers

This Korean brand has been manufacturing air and water cleaning appliances for 40 years. They produce some of the best air purifiers.

If you’re looking for models with more features than Honeywell models offer, such as air quality sensors and automatic speed control, then Winix has some excellent options.

Their latest models are competitively priced, but we especially like going for last year’s models which can be bought at a bargain. Last time we checked, the Winix 5500 was going for only $139.99 on Amazon, making it possibly the best value air purifier available in the market.

For air purifier reviews and recommendations, see our Best Air Purifier Reviews.

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