Portable air cleaners, also known as air purifiers, are devices that remove air contaminants from indoor air. It is important to choose a portable air cleaner that will be effective in removing the air contaminants in your space and won’t add other air contaminants.
Before purchasing, do some research. Start with a list of models that are top-rated or available near you. Then consider the four basic criteria below. It can be difficult to find some important information on a product website. You may need to ask the manufacturer customer service for some information.
When choosing a portable air cleaner for your home, classroom, workplace, or other space, consider these four basic criteria:
- Filter Only – No Ionic, Ozone, or Ultraviolet (UV) Technologies
- High Efficiency Particulate Air (HEPA) Filter
- Right Size for Your Room
- Not Too Loud
Read more about these criteria below. Once you’ve chosen a portable air cleaner, learn how to use a portable air cleaner.
1. Filter Only – No Ionic, Ozone, or UV Technologies
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 These Technologies
- Ozone generation
- Ionization
- Ion generation
- Plasma technology
- Ultraviolet (UV) light
- Germicidal or disinfection technology
- Essential oil diffuser
- Electrostatic precipitation
- Photocatalytic oxidation
Why This Is Important
"Mechanical" portable air cleaners only use physical filtration, such as pleated or HEPA-style filters. Mechanical portable air cleaners with a HEPA filter are highly effective at removing indoor air contaminants.
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. HEPA Filter
What To Look For
Not all filters are HEPA (High Efficiency Particulate Air) filters. Choose a HEPA filter to effectively remove small particles.
How To Do This
Avoid devices that advertise "HEPA-like," "HEPA-style," or "99% HEPA."
A HEPA filter should remove 99.97% of 0.3 μm size particles. Check the technical specifications or ask the manufacturer customer service for this information.
In addition to a HEPA filter, look for a carbon filter to remove some gases like volatile organic compounds (VOCs). Keep in mind that these filters generally need to be replaced more often.
Note that HEPA and carbon filters are not washable or vacuumable. However, a pre-filter may be washable or vacuumable. If a device advertises a washable or vacuumable HEPA or carbon filter, look for another device.
3. Right Size for Your Room
What To Look For
Find a portable air cleaner sized to clean your room.
How To Do This
Use the Clean Air Delivery Rate (CADR)
Look for a device that lists a “tobacco smoke” or “smoke” Clean Air Delivery Rate (CADR). The CADR is different than the “square footage” or “floor rating” of an air cleaner. If a device only lists coverage for a room square footage, and the manufacturer cannot provide you with documentation of the smoke CADR, look for another device.
Choose a device with a smoke CADR equal to at least 2/3 the area of the room where you’ll use it (width × length, in feet) (Table 1). The CADR should be listed in cubic feet per minute (CFM). For example, for a room that is 20 feet wide and 20 feet long, the room area is 400 square feet. For a room of this area, choose a portable air cleaner with a CADR of at least 267 CFM.
If you’re in an area that often has heavy wildfire smoke, consider a higher smoke CADR, closer to the area of the room.
The CADR is a standard for measuring a portable air cleaner’s efficiency that was developed by the Association of Home Appliance Manufacturers (AHAM). It is best to find a device that lists an “AHAM Verifide" CADR. However, if a device lists a smoke CADR but has no AHAM Verifide sticker, it is possible that the CADR was measured another way. Ask the manufacturer customer service for documentation of their CADR claim.
Larger or Open Rooms
If a room is bigger, has an open floor plan, or doors are kept open between rooms, consider getting two portable air cleaners. 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. Even lower CADR devices will remove some amount 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.
Consider creating a cleaner air room. Watch a video and learn how to create a cleaner air room, EPA.
Recommended Portable Air Cleaner Sizing (5 Air Changes per Hour, ACH)
| Room Area square feet, with 8 foot ceiling | 200 | 300 | 400 | 500 | 600 |
|---|---|---|---|---|---|
| Approximate CADR (cubic feet per minute, CFM) | 133 | 200 | 267 | 333 | 400 |
Use this table to determine the size of air cleaner that is large and efficient enough to clean your room. Look for a device that lists a “tobacco smoke” or “smoke” Clean Air Delivery Rate (CADR, shown in the top row) equal to at least 2/3 the area of the room. For example, for a 300 square foot room, choose a portable air cleaner that has a smoke CADR of at least 200 CFM.
Why This Is 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
What To Look For
Pick a quiet device. Loud devices could be harmful or may be more likely to get turned off.
How To Do This
The U.S. EPA recommends keeping indoor noise levels below 45 decibels (dB). 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 room or using multiple devices, and running at a lower fan speed. Use the “auto” setting if your device has a sensor and can automatically adjust the fan speed.
Other Considerations
Upkeep and cost: HEPA filters need to be replaced regularly, so check the cost and frequency for replacements. Typical costs are $20-80 per replacement, depending on size. Suggested replacements are often every 6 to 12 months, and a replacement is often needed following a heavy smoke event. Some devices may have multiple filters to replace. A separate, washable or vacuumable pre-filter can improve the lifetime of the HEPA filter.
Energy: Check the Energy Star database, U.S. Department of Energy for more efficient devices, especially for a large facility with many devices.
Tampering: Some devices provide a “child lock” feature that restricts button use.
Footprint: Some portable air cleaners are large or heavy. Before purchasing a device, consider the space it will take up.
Air sensor: A device with an air sensor may have a setting to adjust the fan speed automatically.
Display: A display that can be turned off is helpful 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. Be sure to check noise requirements for your space. 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)
Other Ways to Improve Indoor Air
A portable air cleaner won’t remove all indoor air pollutants. It’s important to remove sources of contaminants and ventilate when outdoor air quality is good. See other ways to improve your indoor air quality.
More Information
Ventilation and Air Quality for Reducing Transmission of Airborne Illnesses (PDF)
Guide to Air Cleaners in the Home, EPA
Air Cleaners for Asthma Programs, Regional Asthma Management and Prevention