What is a Portable Air Cleaner?
A device that removes air contaminants from indoor air, often referred to commercially as an “air purifier.”
What are Indoor Air Contaminants?
Indoor air contaminants may come from outdoor sources like wildfire smoke or traffic-related pollution, or from activities in and around the home like smoking, cooking, vacuuming, or using scented products. Infectious droplets and particles generated from people coughing or sneezing can also contribute to indoor air contaminants.
Portable air cleaners are an important way to remove wildfire smoke, respiratory viruses, dust, and pollen from indoor air. It’s important to keep indoor air healthy. Contaminants in indoor air can cause health effects such as:
- Burning eyes, runny nose, headache, and coughing.
- Aggravation of existing heart and lung diseases, including asthma.
- Mental health concerns and psychological stress.
Choosing a Portable Air Cleaner
Before going to the store, do some research. Start with a list of models that are top-rated or available near you, then consider the four basic criteria below. You may need to ask the manufacturer for important information.
Consider These Basic Criteria
When choosing a portable air cleaner for your home, classroom, workplace, or other space, consider these four basic criteria.
- 1. Filter only – no ionic, ozone, or UV technologies
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What to look for:
Look for a simple mechanical filter device with no other technologies.
How to do this:
- Check that a device is “mechanical” on the List of CARB-Certified Air Cleaning Devices (rather than “electronic”).
- Check the manufacturer's webpage or the device manual.
Avoid technologies such as:
- Ozone generation
- Negative ionization
- Bipolar ionization
- Ion generation
- Electrostatic precipitation
- Photocatalytic oxidation
- Germicidal or disinfection technology
- Plasma technology
- Ultraviolet (UV) light
- Essential oil diffusers
Why is this important?
"Mechanical" portable air cleaners only use physical filtration, such as pleated or HEPA-style filters.
Despite their growing popularity, “electronic” air cleaners use other technologies that produce harmful byproducts like ozone, hydroxyl radicals, formaldehyde, and ultrafine particles. These contaminants have been linked to adverse health effects like worsening of asthma symptoms, lung inflammation, increased blood pressure, and increased risk of cancer.
- 2. A real HEPA filter
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What to look for:
Choose a real HEPA (High Efficiency Particulate Air) filter that efficiently removes small particles.
How to do this:
Avoid devices that advertise "HEPA-like," "HEPA-style," or "99% HEPA." Check the technical specifications for devices that remove 99.97% of 0.3 μm size particles.
In addition to a HEPA filter, look for an activated carbon filter to remove some gases like volatile organic compounds (VOCs). Keep in mind that these filters generally need to be replaced more often.
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- 3. The right size for your room
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What to look for:
Find a portable air cleaner that’s large and efficient enough to clean your room.
How to do this:
Look for a device that lists a “tobacco smoke” or “smoke” Clean Air Delivery Rate (CADR) equal to at least 2/3 the area of the room where you’ll use the portable air cleaner (width × length, in feet). If you’re in an area that often has heavy wildfire smoke, consider a higher tobacco smoke CADR, closer to the area of the room. If a device doesn’t list an “AHAM Verifide" CADR, look for another device.
If a room is bigger, has an open floor plan, or doors are kept open between rooms, consider getting two units. If your ceiling is taller than 8 feet, look for a slightly higher CADR. The CADR is measured at the highest fan speed, so consider finding a device with a CADR for a larger size room, or using multiple devices, and running at a lower fan speed.
Devices with a higher CADR are more effective but tend to be more expensive. However, even lower CADR devices will remove some level of air contaminants. Picking a lower CADR device is preferable to not having any portable air cleaner during a poor air quality event. Consider using your lower CADR device in a smaller room.
Recommended Portable Air Cleaner Sizing
(5 Air Changes per Hour, ACH)Approximate CADR
(cubic feet per minute)133 200 267 333 400 Room Area
(square feet, with 8 foot ceiling)200 300 400 500 600 Image
Why is this important?
The CADR is the best measurement of how well a portable air cleaner removes particles from air. It is the volume of air it can filter in a minute, at the device’s max fan speed. The higher the CADR, the faster it can filter air.
- 4. Not too loud
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What to look for:
Pick a device that’s not so loud that it could be harmful or a nuisance and might get turned off.
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How to do this:
The U.S. EPA recommends keeping indoor noise levels below 45 dB (for reference, 40 dB is roughly the noise level of a humming refrigerator; 80 dB is about the noise level of a leaf blower).
To reduce noise, consider finding a device with a CADR for a larger size room, or using multiple devices, and running at a lower fan speed. Turn down the fan speed for a while if it’s too loud.
Other Considerations
- Upkeep: HEPA filters need to be replaced regularly, so check the cost for a replacement. A separate, washable pre-filter can improve the lifetime of the HEPA filter.
- Energy: Check the EnergyStar database, U.S. Department of Energy for more efficient devices, especially for a large facility with many devices.
- Tampering: Some units provide a “childlock” feature that restricts button use.
- Footprint: Some portable air cleaners are large. Before purchasing a device, consider the space it will take up.
- Air sensor: A unit with an air sensor can adjust the fan speed automatically.
- Display: A display that can be turned off is helpful to use the unit at night.
- Do-It-Yourself: Making your own box fan filter can be a less expensive option to filter air and improve indoor air quality in a single room or designated space. See the BC Centre for Disease Controls’ factsheet on Do-It-Yourself Air Cleaners (PDF).
Spaces Other Than Your Home
There are some additional considerations for spaces such as schools, childcares, adult care facilities, or offices. For example, be sure to check noise requirements for your space. Also keep in mind that upgrading building ventilation systems should be the first priority. Check these resources for more information.
- Improving Ventilation and Indoor Air Quality During Wildfire Smoke Events Recommendations for Schools and Buildings with Mechanical Ventilation (PDF)
- Ventilation and Air Quality for Reducing Transmission of Airborne Illnesses (PDF)
What else can I do to improve indoor air?
A portable air cleaner won’t remove all indoor pollutants. It’s important to remove sources of contaminants and ventilate.
- Avoid adding to indoor air pollution. Avoid smoking or vaping, using fragranced products, or burning candles or incense. Also consider frying and broiling less often.
- Clean regularly with damp microfiber cloths and a HEPA-filtering vacuum cleaner.
- Use built-in ventilation like kitchen and bathroom exhaust fans and whole-building ventilation.
- Open windows and doors daily. Close them if outdoor fine particulate matter (PM2.5) levels are high. You can check current and forecast air quality at AirNow.gov or during wildfire smoke events at the Washington Smoke Information webpage.
- Portable air cleaners aren’t as effective when windows and doors are open, so turn them off while you’re naturally ventilating.
- Update your HVAC system filters to MERV 13 to remove small particles.
- Learn more at our Healthy Home webpage.