How Does an Air Purifier Work?

Are you thinking about purchasing an air purifier, but aren’t sure what exactly they do or how they work? You’re in the right place!

In this proHVACinfo guide, you’ll learn:

  • What air purifiers are
  • How air purifiers work
  • The different types of air purifiers
  • How effective air purifiers are

How do Air Purifiers Work?

In the simplest terms, portable air purifiers (also called “air cleaners” or “air sanitizers”) are devices designed to clean the air in a single room or area of the home.

They do that by taking in air from the surrounding environment, sanitize it by removing particle matter (microscopic pollutants that circulate in the air in your home), and recirculating the clean air.

When it comes to your health and clean air, not all pollutants are equal – size matters!

You might think that larger pollutants are more dangerous, but it’s actually the smallest pollutants (generally considered to be 10 microns in diameter or smaller) that can be inhaled into the lungs and cause damage.

To be more specific, pollutants include particles that made their way indoors from outside and include pollen, mold spores and other allergens.

Pollutants can also be generated indoors from activities such as cooking, burning a candle, or smoking tobacco. Read on to learn about the different types of purifiers.

Different Types of Air Purifiers

There are several types of air purifiers on the market; the most useful way to think about the different types of air purifiers is what they’re meant to sanitize: air particles (such as pollen, dust, and other allergens) or gases and odors (like tobacco smoke).

Air purifier filters are usually designed to filter either particles or gases, so if you’re looking for protection from both, you’ll want an air purifier that has more than one type of filter.

Particle Air Filters

The basic functionality of these filters works how you’d expect; air is sucked into the purifier from the room, the particles are caught in the filter, and the clean air is recirculated.

Some air purifiers include a “pre-filter”, which is designed to capture the largest pollutants.

Pre-filters capture allergens like pet fur.

They’re useful additions in most air purifiers because they let the primary filter focus on smaller pollutants, and also help lengthen the life of the primary filter.

An important number to understand when it comes to filtered air purifiers is the Minimum Efficiency Reporting Value (“MERV”).

A filter’s MERV measures how small of a particle the filter can remove from the air. MERV filters are ranked on a numeric scale ranging from 1-16, with higher numbers being better.

Filtered air purifiers that meet an even more rigorous set of criteria earn the designation of a HEPA filter, which stands for “high efficiency particle air” filter.

These super-efficient filters have MERVs ranging from 17 – 20, and are typically made of fiberglass that is twisted and interlaced.

HEPA filters, by definition, are able to remove at least 99.97% of particle matter with a size of 0.3 microns (over 30 times smaller than the particle matter described above).

Anything larger than 0.3 microns is caught even more often.

Performance of air purifiers is also measured with the Clean Air Delivery Rate (“CADR”), which is expressed in cubic feet per minute.

Simply put, the CADR tells you the volume of air filtered each minute by the purifier.

This measurement is meant to help consumers understand the effectiveness of their air purifier and compare options.

When shopping for an air purifier, the CADR you need is determined by the size of the room or area you want to sanitize. Check out the table below for recommended air purifier CADRs based on room size!

Source: EPA

One thing to keep in mind is that home HVAC systems also come with a filter that helps keep pollutants out of the air.

HVAC filters work in a similar manner, but they usually aren’t sufficient on their own to keep the air in your home high quality.

HVAC filters only run while the unit is actually running, which is typically less than 25% of the time even in hot or cold seasons.

You could keep your HVAC system running all the time, but that would quickly run up your electric bill! You’ll likely find that air purifiers are a lower-cost alternative.

Some air purifiers have reusable filters. As their name implies, rather than replaced, these filters are simply washed and reused.

For that reason, they are typically a cheaper option in the long run, but must be carefully maintained to preserve their efficiency and useful life. All air purifiers with filters require some maintenance (either being replaced or cleaned), and you should follow the manufacturer’s recommendations in each case.

Activated Carbon Filters

Activated carbon filters (also known as activated charcoal filters) work on a molecular level to remove odors and pollutants that a filtered purifier won’t catch.

The bonding property of the chemicals in activated carbon filters makes them the perfect choice to sanitize gases and tobacco smoke from the air.

Carbon filters can be particularly helpful to individuals with multiple chemical sensitivity (“MCS”), because they filter formaldehyde, a gas commonly used in household products that can cause problems for individuals with MCS.

Do Air Purifiers Work?

With all the conflicting information out there, it can be difficult to determine how effective air purifiers are, and even whether they work at all!

The good news is that, yes, air purifiers can be an effective and reliable way to remove particle matter and gases from your home. However, there are some limitations you should understand.

The first thing to understand is that, according to the EPA, the most effective ways to improve your indoor air quality is to remove the sources of pollutants and ventilate the home with fresh outdoor air (concentrations of pollutants can be five times higher indoors than outside).

Of course, ventilating with outdoor air isn’t always practical (like on very hot or very cold days), and in some cases, such as a pollen allergy, it might just make things worse.

The next thing to understand is that air purifiers are only able to clean the air that is freely circulating throughout your home.

Once pollutants have settled to the ground or on furniture in your home, the air purifier is less likely to be of use.

For that reason, air purifiers aren’t able to sanitize all the air inside your home.

Finally, it’s important to understand that air purifiers are only able to clean the air in the room or area in which they’re located.

Purifiers with a higher CADR are able to sanitize air for larger square footage, but a single air purifier isn’t able to clean all the air throughout your home (there are “whole-house” air purifiers, but those are typically built into the home’s HVAC system or incorporated into the ductwork.

Having said that, portable air purifiers can be an effective supplement to help improve the quality of the air in your home. In fact not only do air purifiers remove particle matter, several studies using portable HEPA air cleaners have also demonstrated improvements in cardiovascular health.

Final thoughts on air purifiers

The first step toward maintaining sanitary air throughout your home is try to remove the particle matter at its source.

That process, combined with natural ventilation from outdoor air, can be effective in maintaining clean and healthy air indoor, but isn’t always enough to keep the air in your home clean.

Air purifiers can effectively supplement this process and may also provide other health benefits.

If you are primarily concerned with removing particles like dust or pollen, consider an air purifier with a filter, keeping in mind your desired HEPA rating (efficiency / effectiveness) and CADR rating (volume of air cleaned / square footage covered).

If you’re primarily concerned with gases or odors, an activated charcoal filter may be your best bet.

Thank you for reading and we hope you now understand more about what an air purifier does and how air purifiers work!

Stephen Marks

Stephen Marks

Stephen is an HVAC and home-repair enthusiast. He's here to answer any of your questions about HVAC!

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Stephen Marks

Stephen Marks

Stephen is an HVAC and home-repair enthusiast. He's here to answer any of your questions about HVAC!

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