Take a deep breath—if you can. Many of the things we do to keep energy costs down, such as fixing drafty doors and leaky windows, can also seal in pesky pollutants and irritants. Many people who buy air purifiers do so in hopes of easing asthma or allergies. But despite product claims, there’s little definitive medical evidence that air purifiers help to relieve respiratory symptoms.
Improving indoor air quality starts with minimizing pollutant sources such as cigarette smoke, dust, and pet dander. We test how well a room air purifier removes dust and smoke from an enclosed space, how it performs at high and low speeds, and how quiet it is.
The very best portable models we tested were effective at cleaning the air of dust, smoke, and pollen at their highest and lowest speeds. The worst models weren’t terribly effective at any speed.
How We Test Air Purifiers
At Consumer Reports, all our air-quality testing is conducted in a 12x18-foot sealed room isolated from the rest of our labs. To test how well air purifiers clean the air, we place the air purifier in the center of the room and inject cigarette smoke and dust into the room through a tube. We then use a machine that analyzes the particles in the air and measure the change in the air particle concentration over a 15-minute period at both the air purifier’s high and low speeds.
To measure noise, we use a decibel meter at ear level 4 feet in front of the air purifier and record the noise level at high and low speeds for each model. Annual cost is a combination of filter replacement costs and the energy required to run the purifier 24 hours a day for an entire year.
Breathe Easier
Before you resort to buying an air purifier, try some simple steps to reduce indoor air irritants, including:
Before you resort to buying an air purifier, try some simple steps to reduce indoor air irritants, including:
- Vacuum often and thoroughly using a vacuum with high-efficiency particulate air (HEPA) filtration.
- Ban smoking indoors.
- Maintain your heating and cooling equipment, and change air filters regularly.
- Minimize the use of candles and wood fires.
- Use exhaust fans in kitchen, bath, and laundry areas.
- Don’t store chemicals, solvents, glues, or pesticides near your living quarters.
- If pollen or related allergies keep you from opening windows, run your air conditioner or forced-air cooling system with a clean air filter.
- Prices: $50 to more than $1,000.
Room Air Purifier Features
- Washable prefilter: A washable—and reusable—prefilter collects large particles; it can help cut overall costs. However, many of our higher-rated models did not have this option.
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Pros: They’re portable—most room air purifiers weigh from 10 to 20 pounds, have a handle, and stand on the floor or on a table. Heavier models might have wheels.
Many have a HEPA filter, which can capture ultrafine particles. Keep in mind that most of these filters need to be replaced annually, an expense that might approach the cost of the air cleaner, but a few models are now available with cleanable HEPA filters.
Cons: Portable models that use either electrostatic precipitator or ionizer technology could produce some ozone, a lung irritant.
Electrostatic precipitator and ionizer air purifiers should not be confused with dedicated ozone generators, which produce large amounts of ozone by design. Ozone generators should be used only by professionals to reduce odors, germs, and mold. Ozone is a serious health concern, prompting the state of California to ban the sale of ozone generators (and other air purifiers that emit more than 50 parts per billion of ozone) from the general market.
Operating Costs
Many portable models have annual operating costs of $150 to $200 for filter replacement and electricity (with the majority of that cost being for filters). Filter prices can generally range from around $10 to about $100 (though some are priced well into the hundreds). Some units use a prefilter to capture large airborne particles before they reach the HEPA filter, possibly extending its life.
Depending on usage, you typically need to replace the carbon filters every three months and the main filter yearly. To cut costs, look for room models that are Energy Star certified, meaning they are relatively energy-efficient compared with standard models. Some models have washable filters that can be reused.
Keep It Clean
Any air purifier won’t work well if the filter is clogged and dusty, and if the filter is full, it may stop working entirely.
Quietness Counts
Noise level is important, especially if you run an air purifier in a room where you sleep or work. For the sake of efficiency (and quietness), we recommend picking a larger unit and running it on a lower speed, rather than cranking up a small one. Having a larger unit can also accommodate those times when you need to clean a room quickly, such as when cooking odors escape the kitchen exhaust hood.
Check Out the Best Air Purifier
Fan: Most room air cleaners use a fan to suck in air for filtration. Those without a fan (the air circulates naturally throughout your home) run more quietly, but those we tested without fans worked poorly.
Servicing indicator: A clogged air cleaner works inefficiently. This feature lets you know when the unit needs to be cleaned or the filter replaced.
Programmable timer: These controls allow you to set the purifier to run a few hours before you’ll be using a room, or to turn it off automatically.
Carrying handle: This makes it easy to move unit from room to room.
Number of speeds: The unit adjusts to your air-cleaning needs—lower when you are sleeping or working and need quiet, higher when it’s prime pollen time.
Ionizer: If a unit has an ionizer (which attracts particles via an effect like static electricity), it’s important that it not produce ozone. It may say on the box or in an operation manual whether it produces ozone; you can also check our ratings. Ozone is a lung irritant.
Remote control: This lets you easily adjust settings from across the room.
Dirt sensor: In some room models, the unit automatically adjusts fan speed to the level of dirt or dust in the air.
What They Do Well
The better air purifiers are especially good at filtering pollutant particles such as dust, smoke from candles or fireplaces, and pollen.
What’s Not So Great
Volatile organic compounds from adhesives, paints, and cleaning products, and other types of gaseous pollutants, however, are another matter. Some portable models with carbon prefilters are claimed to filter VOCs, but the Environmental Protection Agency warns that such filters are specific to certain gaseous pollutants, not for others, and that no air purifier is expected to remove all gaseous pollutants found in the typical home. Carbon filters also must be replaced often, typically every three to six months, or they stop working.
What the Terms Mean
The Association of Home Appliance Manufacturers certifies most room models as part of a voluntary program that includes appropriate room size and maximum clean-air delivery rate, a measure of cleaning speed. We judge a CADR above 350 to be excellent and below 100 to be poor. Choose a model designed for an area larger than yours for better cleaning at a lower, quieter speed.
