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What Does an Air Purifier Do?

By: Sheryl Cannes
Updated on: April 05, 2024

Smoke, VOCs, pollen, and pet dander are only a few of the impurities that could be floating through your home or office. Air purifiers target different impurities, particulates, or contaminants, removing them from a room’s breathable air for a cleaner atmosphere.

However, not all air purifiers do the same thing. Different types of filtration and purification systems target different types of particles and contaminants.

Air Purifiers Filter Air Pollutants

If you have allergies, you’re probably already well aware of common allergens. Yet, there is a wider range of airborne particles that affect your lungs and air passages. We put together a list of common air pollutants that affect indoor air quality and the health issues they can cause.

  • Dust/dust mites: Dust, or more accurately dust mites, are a fairly common allergen. They eat shed human skin cells found in household dust. These microscopic bugs love warm, humid environments like that found in a mattress or bathrooms. Symptoms of a dust mite allergy are similar to those of other allergens that inflame the nasal passages. You might experience a runny, stuffy nose, itchy and watery eyes, and general nasal congestion.
  • Pollen: Trees, grasses, flowers, and other foliage release pollen at various times throughout the year. These seasonal allergens can lock some people away in their homes for months. Some pollen is visible, leaving yellow, powdery dust everywhere. Other pollens are so small they’re nearly undetectable by the naked human eye. Like dust mites, pollen causes general nasal congestion, red itchy or swollen eyes, and the general feeling that you have a head cold. Some people may also develop a skin rash in areas where the pollen comes into contact with the skin.
  • Pet dander: Pet dander are the dead skin cells shed by animals. In the home, cats and dogs are usually the culprits, but people can develop allergies to any kind of pet dander. Pet allergy symptoms are similar to other allergic reactions like hayfever, with general head congestion, runny eyes, and postnasal drip.
  • Mold: Mold quickly develops in warm, humid climates. If you’ve spotted mold around your windows or noticed a musty odor, mold could cause respiratory issues. Mold can make you feel like you have the flu or a cold, and air filtration systems can have a hard time filtering spores. These invaders irritate the air passages, causing congestion, general fatigue, and headaches.
  • Off-gassing/fumes: Many common household items off-gas or release fumes. Paint, adhesives, and some cleaners can have fumes that irritate the airways or simply smell bad.
  • Pesticides: Pesticides and any number of other chemicals can find their way into the home. Formaldehyde, benzyne, styrene, and toluene are a few of the more common indoor air pollutants that enter the home through pesticides.

Types of Air Purifiers

Different types of air purifying systems remove different types of air contaminants. You can determine the right purification system for you based on where you live and any medical conditions you may have like asthma. For example, some areas of the country are richer in certain types of pollen than others. Clean air starts by knowing the kind of purifier and filter system you need.

Mechanical Filters (HEPA)

You’re probably more familiar with mechanical filters than you realize. These air purifiers pull air through a filter made of densely woven fibers arranged in an accordion shape. The fibers capture air particulates, removing them from the air. High-efficiency particulate air (HEPA) filters or true HEPA filters are some of the most powerful mechanical filters, removing 99.97 percent of all particulates down to those that are .3 microns in diameter. That level of filtration not only removes pollen and dust and some gasses and odors.

Mechanical filters eventually get saturated and need replacement. Some filters are washable and reusable, while others are disposable. Washable filters save you money over the lifetime of the air purifier.

Activated Carbon

Activated carbon (or carbon activated) filters absorb substances into open pores between carbon molecules rather than trapping them like a mechanical filter. The activated carbon has thousands of tiny pockets that absorb odors and some gases. Unfortunately, they don’t absorb all gases. For example, they can’t absorb fumes from ammonia or formaldehyde, so they’re useful as long as you know their limitations.

Activated carbon filters are often coupled with other forms of filtration to increase the air purifier’s efficiency. That may include negative ion technology, ultraviolet light technology, or a HEPA filter.

Ultraviolet Germicidal Irradiation (UVGI)

Ultraviolet germicidal irradiation, sometimes called UV technology, works by killing bacteria, viruses, and mold spores with ultraviolet light. The UV light must stay in contact with the contaminant for minutes to hours, which many air purifiers cannot accomplish. While this type of air purification can kill some harmful substances, alone it doesn’t entirely remove unwanted pathogens.

UVGI purifiers can also emit potentially dangerous ozone. Ozone molecules have three oxygen atoms and can cause shortness of breath and lung irritation.

Photocatalytic Oxidation (PCO)

PCO purifiers combine ultraviolet rays with a photocatalyst to oxidize gaseous pollutants with hydroxyl radicals. This chemical reaction removes some pollutants but can have a harmful reaction and produce ozone.

Electrostatic Ionizers (Negative or Positive Ions)

Negative or positive ionizers produce charged particles that attach to smaller particles. The ions’ added weight either causes the particles to attract to a plate on the air purifier, or they fall to the floor or onto furniture, where they can be picked up with a dust cloth or vacuumed. These air purifiers also have the potential to create ozone.

Ozone Generators

Ozone generators emit ozone molecules that change the chemical composition of certain substances, which removes them from the air. But they are not a recommended air purifier for various reasons. Ozone is one of the main components of smog. Introducing it into an indoor area can actually decrease the air quality and cause breathing problems.

Whole House Purifiers

Whole house purifiers connect to the HVAC system, removing impurities and contaminants as air circulates through the home. These systems are expensive but are a good option for those with severe allergies or asthma. They don’t remove germs but make a big difference in the home’s overall air quality rather than affecting only a single room.


Can air purifiers remove volatile organic compounds (VOCs)?

Air purifiers with activated carbon filters can remove VOCs. But they cannot remove all VOCs, only lower the amount in the home.

What is a clean-air delivery rate (CADR)?

The Association of Home Appliance Manufacturers (AHAM) certifies and verifies the air purity claims of manufacturers. Particle size, percentage of particles removed, and volume of air moving through the purifier are all used to determine the air purifier’s CADR. The higher the CADR, the better and more effective the air purifier. A good baseline is that the CADR should be twice the fan speed’s power. If an air purifier uses 50 watts at the highest speed, it should have a CADR of 100.

Does it matter where I place my air purifier?

Air purifiers work better under certain conditions. Because many air purifiers have an exhaust fan, they need to have plenty of space between them and walls and furniture for the best air circulation. They should also be placed away from other electronic devices, interrupting how the air purifier functions. Be careful to put the air purifier where it won’t interfere with the room’s traffic pattern as well.


Do air purifiers work—yes. At their most basic, purifiers use various air filters to remove specific types of particles from the breathable air. However, the type of particulates they remove and how they remove them make a difference in how the purifier functions in your home. Your unique circumstances and needs determine which air purifier type will be most effective for you.


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