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With ever-increasing wildfires that are larger and more destructive than in the past and rising concern over health risks associated with indoor air pollution from sources like gas stoves, air quality seems to be on people’s minds more than ever before. One potential solution for getting rid of contaminants in your home is an air purifier.
Before you start researching the best air purifier to buy, it’s important to understand what they can actually do and what you should be looking for depending on your particular space and risk factors.
Do air purifiers work?
The short answer is yes, but that doesn’t mean they’re capable of clearing any and all pollutants or germs out of the air indoors. (Although air cleaners do help block the COVID-causing virus, research suggests.)
A 2018 technical summary by the Environmental Protection Agency evaluated various studies to conclude that air cleaners operating in homes consistently reduce exposure to indoor particulate matter that is 2.5 to 10 microns in size. For reference, the smallest particles visible to the human eye are generally in the 50- to 60-micron range; a human hair is around 75 microns, pollen is 5 to 11 microns, dust is 0.5 to 3 microns, and tobacco smoke is around 1 micron or smaller.
Very small particulate matter can adversely affect the cardiovascular system because when you inhale them, they can travel deeper into the lungs than larger particles.
Essentially, air purifiers can reduce particles floating around indoors, though the actual health benefits of that reduction may not be as substantial as you’d hope. The EPA summary states that most studies have found a link between portable air cleaners in homes and at least one marker of improved health, although the improvements are typically modest.
How well an air purifier works also depends on proper use, meaning that it’s appropriate for the size of the space, placed correctly (not in some corner behind a curtain), has a certified filter that’s cleaned or changed as needed, and is run continuously with doors and windows closed.
“The amount of time that an air cleaner operates influences its ability to reduce pollutant concentrations and associated health risks,” according to an EPA report. “If they are not operating, they will not be effective.” While adequate ventilation is also helpful in maintaining cleaner indoor air, the free flow of air will make it more difficult for an air purifier to achieve the desired results.
In order to measure the actual efficacy of air purifiers, the Association of Home Appliance Manufacturers (a private voluntary standard-setting trade association) developed the clean air delivery rate, or CADR, which is a measure of how much clean air a portable air purifier delivers measured in cubic feet per minute (cfm).
The EPA says the CADR is the most helpful parameter for understanding the effectiveness of portable air cleaners.
“The testing program is very simple,” said Jill Notini, vice president of marketing and communications for the Association of Home Appliance Manufacturers (AHAM). “It looks at tobacco smoke, dust, and pollen, and the reason why is because those are three different particle sizes, so they’re good representatives for a small particle, a medium particle, and a larger particle.”
The higher the CADR number for each pollutant, the faster the unit filters the air. As a general rule, AHAM advises that each CADR number of your air cleaner should be equal to at least two-thirds of the room’s area. For example, the AHAM website says that a room with the dimensions of 10 feet by 12 feet, or an area of 120 square feet, should have an air cleaner with a smoke CADR of at least 80.
Aside from evaluating particle capture, their testing also looks at the fans and motors in these machines to see how much air they’re able to pull in and keep moving through the filters. The CADR includes both the removal efficiency for a particular pollutant and the device’s airflow rate.
Notini said that pollen is one of the largest particles and smoke is one of the smallest, measuring in at 2.5 microns, aka a very fine particle that you can’t see but can easily inhale. She also said that AHAM will be releasing a new standard for the removal of germs like fungi, bacteria, and viruses (which people are looking for increasingly in the age of COVID). It’s also working on a chemical standard to include in its evaluations in the next few months.
In a 2020 study published in the International Journal of Environmental Research and Public Health, researchers set up real and sham air purifiers in the homes of 32 healthy people and compared the air quality and volunteers’ lung function during different four-week periods. They found having an air purifier reduced the indoor 2.5 microns particulate matter level by about 11%, but the result was only statistically significant in the homes of single people (possibly due to fewer doors opening and closing and less activity in general). The air purifiers didn’t seem to improve lung function or reduce airway inflammation.
It’s possible air purifiers could be more helpful in homes of people with pets, smokers, higher-risk individuals, or those with a different model of air purifier, since effectiveness does vary from product to product. This study may also have been too brief to detect an impact on health. The CDC looked at data from multiple studies and concluded that portable air cleaners, particularly those with HEPA filters, are effective in reducing exposure to air pollutants produced by wildfires and can potentially limit the negative health impacts from that exposure.
Dr. David Rosenstreich, the director of Allergy and Immunology at Montefiore Medical Center, explained that since dust is one of the larger particles, it tends to settle on surfaces, which makes it harder for an air purifier to suck in and capture.
He recommends air purifiers more often for people with pets or who have a mold issue, since animal dander and mold spores are the most common allergens that float through the air.
Air purifiers require some upkeep so that they continue to function as intended. Studies have shown that after an initial period of use and enthusiasm, the devices are often not maintained properly, operated less frequently, turned off completely, or put into storage because people are annoyed with the noise or other factors, according to the EPA.
That’s one good reason you should consider every possible feature when choosing an air purifier and try to find one that meets your needs. If it ends up in a closet after a month, it will be a waste of money.
How to choose the best air purifier
The priority in selecting an air purifier should, of course, be its effectiveness in cleaning air. But there are many different kinds of air purifiers with similar CADRs, so think about the other features that will encourage continued use.
One popular feature is a HEPA (high-efficiency particulate air) filter, which has deep pleats and a large surface area to help remove fine and ultrafine particles more efficiently. Air purifiers that have HEPA filters are probably the most popular and effective products on the market. (Rosenstreich recommends them exclusively.) However, they also have to be changed after 12 months or 8,760 hours of use.
If you tend to forget about things like changing filters, the alternative may be an air purifier with an electrostatic precipitator, which has a metal plate that charges particles so they become attracted to a plate with the opposite charge. Since the particles stick to the plate, you can simply remove it, clean it, and pop it back in instead of buying replacement filters, Notini said. Some of these types of air purifiers can produce low levels of ozone, which is a lung irritant, so they may not work for everyone.
Other air cleaners use combined technologies to increase their filtration. They may have activated carbon or charcoal filters to help remove gases and odors.
They can also have germ-killing features, like a UV light, to help reduce any bacteria or viruses that may get caught in the filters. It’s also common for air purifiers to use a pre-filter, which is generally a thicker flat or paneled filter that’s helpful in capturing larger particles, along with the main filter. These filters need to be replaced more frequently, but some varieties are washable for repeated use.
After deciding on a filtration system, experts agree that the most important consideration is the size. If it’s more powerful than necessary for a small room, the sound may be too loud and intense; if it’s too small, it won’t work properly.
Products should be labeled with a CADR based on the size of the room they’re suitable for, so you should know the measurements of your space before shopping around. It’s also important to note that the label will indicate the highest possible CADR, which typically occurs only at the highest (and likely loudest) airflow setting. It will have a separate score for each pollutant measured (dust, pollen, and tobacco smoke), which allows you to make sure it does the best job of eliminating the particle you’re concerned about.
You can look out for the AHAM seal of approval, though there are other CADR evaluators, so just read the fine print to make sure it’s legit.
Once you’ve determined your room size and CADR requirements, you should think about noise level and aesthetics. Since it should be placed in a high traffic area to address the densest levels of contamination and odor, it probably shouldn’t be overwhelmingly noisy or unpleasant to look at. Notini said that companies have done a lot of work on sound and design to make air purifiers that are not only functional, but also quieter and aesthetically pleasing.
Note what the labels or reviewers say about sound. Some products even have videos online so that you can hear exactly how loud they are at various settings. The designs are more of a personal preference, but there is a very wide range of shapes, colors, and general vibes on the market. These are some of the best options we’ve found, all things considered.