Indoor Air Cleaners at Home, School, and Commercial Settings

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air filter, air cleaner, replacing filter

Air cleaners can help improve air quality by reducing indoor air pollutants. There are many types, and no single one can remove all indoor air contaminants. Your choice of air cleaner depends on the air contaminant you are trying to control. This webpage provides information to help you choose the right air cleaner based on the contaminants you want to remove.

Air Contaminant Basics

Particulate Matter

Particulate matter (PM) is tiny particles of solids or liquids in air that come from indoor activities such as cooking, cleaning, burning candles, tobacco smoke, and operating fireplaces. These particles can include dust, pollen, mold, animal dander, and other common allergens. Particle pollution can also enter the home from outdoor sources such as fires, road construction, and vehicle exhaust from heavy traffic.

Infectious Aerosols

Infectious aerosols are particles in the air that can cause infection, like bacteria, viruses, and fungi. These come from infected people who may release them into the air (like spreading the flu or coronavirus). Infectious aerosols can also come from in-home sources like mold, which can release fungi into the air.


Gases like carbon monoxide, ozone, nitrogen dioxide, radon, and volatile organic compounds (VOCs) like formaldehyde, are also common indoor air pollutants. Some gases can come from stoves, furnaces, and other appliances that burn fuel. Building materials, carpets and flooring, paints, solvents, cleaning products, aerosol sprays, deodorizers, personal care products, office equipment, and pesticides are also sources. Other gases like ozone or radon can enter the home from outdoors.

Types of Air Cleaners

There are two main types of air cleaners:

  • Whole house/building centrally-located heating, ventilation, and air conditioning (HVAC) systems that use air ducts to distribute air throughout a building.
  • Portable devices that you can move and are designed to filter air in a single room.

Both use various technologies, depending on the design and what air contaminant they remove.

HVAC or Central Air Systems

HVAC and central air systems typically have filters to protect fan motors from dust and debris. Air filters that remove particulate matter and infectious aerosols also can be installed. The Minimal Efficiency Reporting Values (MERV) rating evaluates an air filter’s ability to remove particles. MERV ratings range from 1-16. The higher ratings will remove both large and small particles. The International Organization for Standardization (ISO) also sets standards for filters.

Use filters with a MERV 13 rating or higher or an ISO ePM1 filter. These work best to remove fine particles and infectious aerosols from the air.

Many residential HVAC systems don’t support higher-rated filters. Using the wrong filter can damage your system or reduce air quality. Always check your manufacturer instructions to find out which filters are recommended. Some systems may require upgrades to use higher-rated filters.

Filter Rating Systems for HVAC Systems

This table can help you choose the proper filter rating depending on your needs.

MERV ISO 16890 Particle Size (micrometers) Particle Type
1 - 8 ISO Coarse greater than 10 Dust or Pollen
9 - 10 ePM10 3.0 - 10 Dust or Mold Spores
11 - 12 ePM2.5 1.0 - 3.0 Mold Spore, Pet Dander or Bacteria
13 - 16 ePM1 0.3 - 1.0 Smoke or Viruses

The filter you choose depends on what size particles you are trying to remove and what filter ratings your system can handle. If you want to reduce particles like mold spores, pet dander, or bacteria, choose an ISO ePM2.5 or MERV 11-12 filter. Removing tobacco smoke or viruses requires an ISO ePM1 or MERV13 or higher-rated filter. Many systems have switched to MERV13 or higher filters to provide a key layer of protection against spreading illnesses such as coronavirus or flu. An ISO coarse or MERV 6-8 filter is good for reducing dust from activities like construction or general housekeeping. Review the manufacturer’s label and instructions to check that the filter you select is appropriate for your system.

Portable Air Cleaners

People who don’t have HVAC systems may consider using portable air cleaners. These work best to improve air quality in a single room.

Portable air cleaners are sized based on the amount of air they can filter in the room. A rating system developed by the Association of Home Appliances Manufacturers (AHAM) can help you select the right sized air cleaner.

AHAM tests air cleaners and reports their Clean Air Delivery Rate (CADR), the volume of air per cubic feet of a room it can filter in a minute. CADR is established for three-sized particles from smallest to largest: tobacco smoke, dust, and pollen. Look for the “AHAM Verifide” mark that shows that the air cleaner was independently tested. Check the latest list of certified portable air cleaners.

When selecting a portable air cleaner:

  • Use the Air Cleaner Technologies Table to select the right technology for your needs. No air cleaner can remove all air pollutants.
  • Follow advice from the retailer, manufacturer, or AHAM's air filtration standards for the right-sized air cleaner for your room.
  • Place the air cleaner near the center of the room. This will avoid blocking airflow, which can happen if it’s against a wall, in a corner, or under a table or surface.
  • Follow the air cleaner manufacturer’s instructions for maintenance, filter replacement, and cleaning.
  • Portable air cleaners can be noisy so pay attention to noise level information when selecting an air cleaner.

Air Cleaning Technologies

Air cleaners use different technologies: filtration, electrostatic precipitation, ionization, ultraviolent germicidal irradiation, adsorption, photocatalytic oxidation, plasma, and ozone generation.

Air cleaning technologies can be either subtractive or additive.

  • Subtractive technologies remove contaminants from the air without adding contaminants to the air.
  • Additive technologies add substances, like ions, ozone, or radiation to the air to chemically alter or remove air contaminants.

This table can help you select the right air cleaner technology based on the contaminant you are trying to remove.

Air Cleaner Technology Targeted Contaminant Subtractive or Additive
Filtration Particulate Matter Subtractive
High efficiency filtration Particulate Matter and Infectious Aerosols Subtractive
Ultraviolet Germicidal Irradiation Infectious Aerosols Additive
Electrostatic Precipitators Particulate Matter Additive and Subtractive
Ionizers Particulate Matter Additive
Adsorption Media Gases Subtractive
Photocatalytic Oxidation Gases Additive
Plasma Gases Additive
Ozone Generators Gases Additive

We recommend using subtractive technologies like filtration to remove particles. High efficiency particulate air (HEPA) filters can remove many types of particles including infectious aerosols and smoke. Absorbent media such as activated carbon is the best approach to remove gases from indoor air.

Many additive air cleaning devices haven’t been rigorously tested and can create harmful byproducts. For example, some air cleaners can produce ozone, which can aggravate asthma and cause respiratory symptoms. Others may produce charged ions that may help remove particles, but can also create harmful byproducts like formaldehyde and ultrafine particles. See EPA’s Residential Air Cleaners: A Technical Summary and the National Academies of Science, Engineering and Medicine’s report Why Indoor Chemistry Matters for more information.

Schools should review the New York State Education Department Statement Regarding Ionization Air Cleaners for more information about concerns associated with these technologies.

Other Ways to Reduce Indoor Air Contaminants

Remember, air cleaners are not the only way to remove indoor air contaminants. Before you decide to buy an air cleaner consider these strategies:

Reduce the Source of Contamination

Smoke outside. Use paint and adhesives, sealants, and coatings designed for indoor use. If possible, keep new carpets, cabinets, and building materials outside for a few days.

When You Can’t Keep Air Pollutants Out

Ventilate your room by increasing the amount of fresh air. Open windows and doors in areas that don’t have HVAC systems. Try and stay out of the room until new paint dries, and new carpets, cabinets, and building materials off-gas and are odor free. Keep your furnace and other combustion devices in good working order and properly vented. 

Sometimes bringing in air can also bring in outdoor air pollutants, such as during wildfires. During those times, try to take steps to reduce the amount of outdoor air entering the home by closing windows and doors or changing HVAC setting to reduce the amount of fresh air entering the building. Remember, if it gets hot indoors and you have an air conditioner that can recirculate air, use that setting or find a place to get cool.

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