How do air purifiers work?
Air purifiers are designed to remove indoor air pollution which can be made up of small particles in the air. Indoor air pollution primarily comes from cooking, automobile emissions, dust and fires, and can irritate the lungs or trigger allergic reactions, explained Kenneth Mendez, president of the nonprofit Asthma and Allergy Foundation of America. And according to the Environmental Protection Agency, the air inside our homes can be more polluted than the air outside.
“We take about 20,000 breaths each day and spend 90 percent of our time indoors,” Mendez noted. And with all this newfound time spent at home, reducing exposure to particles that can trigger things like allergies and asthma symptoms is important. “If you live in an area with high outdoor pollution, like a metropolitan city, it’s essential to monitor the air quality in your home,” he added.
Full coverage of the coronavirus outbreak
Do air purifiers prevent coronavirus? No.
Air purifiers do not prevent the spread of coronavirus. Although the CDC reports that coronavirus is primarily spread through person-to-person contact or contact with contaminated surfaces and objects, over 200 scientists have asked the World Health Organization and other groups to acknowledge the spread of the virus through the air. Still it is important to understand that simply filtering airborne particles wouldn’t help stop the spread of the virus, given the small size of coronavirus particles, explained Nidhy Varghese, MD, a pediatric pulmonologist in Texas. The average size of a coronavirus particle is less than the 0.3 micron limit for HEPA filters, she added.
“So even if these microbes make it into the purifier, they may elude filtration,” Varghese said. “The data so far suggests that it is unlikely that air purifiers will help with coronaviruses. Ultimately, the decision to purchase a sanitizing air purifier is a personal decision.”
The difference between air purifiers, air cleaners and air filters
Air purifiers are often conflated with air filters, but they differ slightly, said John McKeon, MD and CEO of Allergy Standards — an organization that certifies products as “asthmas and allergy friendly,” among other things.
- Air filters trap and collect dirt and debris in a filter, and are commonly found in heating and ventilation systems. They can significantly reduce the amount of pollutants, allergens and dust in your home.
- Air cleaners remove more particulate from the air than the average filter, said McKeon. The device consists of a fan to draw air in and a filter to remove particulate from that air. While air cleaners often include filters, they are overall more robust in cleaning the air than air filters. Regardless, most companies will use the terms air cleaner and air purifier interchangeably.
- Air purifiers use a process to “deactivate” airborne toxins like pathogens, McKeon explained. Some purifiers use ultraviolet light sterilization to kill mold and bacteria while others use an electrostatic filter to draw particles to metal plates. Most air purifiers rely on a combination to trap as many particles, gases and bacteria as possible.
What is a HEPA filter?
You’ve likely seen this designation on air purifiers and other products before. HEPA stands for “high efficiency particulate air.” HEPA filters are physical filters designed to clear out at least 99.7 percent of particulates that are 0.3 microns or larger in size. For reference, a micron, or micrometer, is about one twenty-five thousandth of an inch and designated with an μm.
Any air cleaner that has a HEPA filter has been tested and approved by the nonprofit Institute of Environmental Sciences and Technology. This means they are true HEPA. Some filters will label themselves as “HEPA-type” or “HEPA-like,” but these filters are not verified HEPA so may not be as effective. True HEPA filters draw particles in via a fan and trap them in a web of fibers. They perform better than standard filters and have become increasingly popular, says Varghese.
Molekule’s air filters are different from HEPA filters. Regular HEPA air purifiers target airborne particles in the air. Molekule’s filter uses its own patented filter technology: photo electrochemical oxidation (PECO). According to Molekule’s, PECO uses free radicals, or highly reactive atoms, to break down pollutants at the molecular level. PECO filters remove and deactivate common gases, bacteria, viruses and mold in the air, according to the brand. It’s important to note that both Consumer Reports and the National Advertising Review Board have disputed some of Molekule’s filtration claims, specifically about their filter’s superiority to HEPA filters.
Molekule and its PECO filter
Molekule’s air filters are different from HEPA filters. Regular HEPA air purifiers target airborne particles in the air. Molekule’s filter uses its own patented filter technology: photo electrochemical oxidation (PECO). According to Molekule, PECO uses free radicals, or highly reactive atoms, to break down pollutants at the molecular level. PECO filters remove — or deactivate, rather than filter out — common gases, bacteria, viruses and mold in the air, according to the brand.
Molekule worked with researchers at the Lawrence Berkeley National Laboratory (LBNL) to test its new filter technology, which it claims is superior to popular HEPA filters. In a January report, LBNL found the Molekule Air successfully removed volatile organic compounds (VOCs) and ozone, its efficiency rate ranging between “high” and “very high” — summarizing that “the air cleaner has enough capacity to remove indoor gaseous pollutants at levels that are typically present indoors, without producing harmful byproducts.” Jaya Rao, the company’s CEO, told NBC News their air purifiers have already killed — which, as mentioned above, Molekule boasts is different from filtered — other viruses in lab tests.
Consumer Reports disputes some of Molekule’s filtration claims: simply put, that while its air purifier efficiently rids the air of many pollutants, it does so at a slower rate than other air purifiers. Molekule, on its end, challenges CR’s tests on its product, telling NBC News they used HEPA tests on a non-HEPA filter and that, therefore, comparing those results doesn’t provide the whole picture. While HEPA remains somewhat of an industry standard, Molekule’s PECO technology is worth considering.
Benefits of air purifiers
While air purifiers can’t protect you from coronavirus, there are still plenty of benefits to having one in your home. If you already experience irritation from dust or allergens, or have asthma, allergies or other respiratory conditions, it may be smart to invest in an air purifier, says Josh Davidson, MD, an allergy and immunology specialist in California.
“We are all trying to do what we can right now. It’s one of those factors that can only help, given everything that’s happening,” he said. “Don’t run out and buy air purifiers in mass and hoard them like toilet paper, but consider it, especially if you are at higher risk.”
Above all else, the best way to prevent the spread of coronavirus is by washing your hands regularly, cleaning and disinfecting regularly-touched surfaces, wearing proper face coverings and avoiding other people, especially those who have been sick.
How to find the best air purifier for you
Before buying an air purifier, narrow down your specific needs, advised Varghese. For example, maybe you’re looking for a purifier for allergies or to protect you against gases. Or maybe you cook frequently and want a purifier to filter out particles produced from your oven and stove.
Varghese recommends seeking a purifier with a HEPA filter for the best results. It’s equally important to find a filter that’s been independently rated by the Association of Home Appliance Manufacturers, she said. All air cleaners certified by the AHAM and given a clean air delivery rating, or CADR, have been tested in an independent laboratory and across the same metrics.
“We put all products on a level playing field regardless of technology, so consumers can easily compare between products,” said Jill Notini, vice president of communications and marketing for AHAM. “We test for things like tobacco smoke, dust and pollen.”
The higher the CADR rating, the more effective and faster the air cleaner is at filtering the air. Notini advises shoppers to pay attention to the rating when shopping. Davidson also encourages shoppers to pay attention to how often the air purifier will require a replacement air filter and how many square feet the air purifier can clean.
Some air cleaners use electrostatic charges and generate a small amount of ozone as a byproduct, said Mendez. Ozone is very reactive and is effective for removing odors and killing mold. But it can also “can cause health problems at high concentrations,” according to the EPA, which notes that ozone generators are often billed as air cleaners. Selecting an independently-rated air purifier will ensure your air cleaner produces less than the EPA-designated ozone limit of 0.08 parts per million. “By using an independent agency like ours, you can make sure you’re getting the right product,” said Notini.
The best air purifiers to shop in 2020
To give you an idea of what’s out there, here are some of the leading and most popular air purifiers. You can find their cleaning capacities and whether they equip HEPA filters or have been approved by AHAM.
1. Blueair Blue Pure 411 Air Purifier
- Cleaning capacity: 161 square feet
- AHAM approved: Yes
- HEPA filter-equipped: No
The Blueair Pure 411 is one of the best budget air purifiers, though it only purifies smaller spaces. This model is great to have in your home office or living room (which you are likely spending more time in right now). The purifier is compact and comes in different colors to match your room’s decor. This model comes with the brand’s own own HEPASilent technology (which is not the same as an approved, true HEPA filter) and a CADR rating. Besides being affordable, the Pure 411 has low-cost replacement filters and is more energy-efficient than other models.
2. Levoit LV-H132 Air Purifier
- Cleaning capacity: 129 square feet
- AHAM approved: No
- HEPA filter-equipped: Yes
The Levoit LV-H132 removes particles from the air with its three stage filtration system including a pre-filter, true HEPA filter and activated carbon filter. It circulates the air in the room over four times in an hour and is equipped with a built-in smart filter replacement reminder and night light.
3. Molekule Air
- Cleaning capacity: 600 square feet
- AHAM approved: No
- HEPA filter-equipped: No
The Molekule Air has a sleek design and includes two filters, designed to capture pollutants smaller than the average air purifier using PECO technology. Though the Molekule is more expensive than other air purifiers, it boasts hundreds of positive reviews and a new approach to air purification.
4. GermGuardian AC4825 Air Purifier
- Cleaning capacity: 167 square feet
- AHAM approved: Yes
- HEPA filter-equipped: Yes
The GermGuardian AC4825 is a 3-in-1 air purifier that includes a HEPA filter, charcoal and PCO filter, UV-C sanitizer and TIO2 treatment. It is equipped with three speed settings and comes with a filter replacement indicator.
5. Honeywell True HEPA Air Purifier
- Cleaning capacity: 465 square feet
- AHAM approved: Yes
- HEPA filter-equipped: Yes
This model is made for larger rooms, and has a true HEPA filter. Honeywell claims this purifier filters and circulates air up to five times an hour. This model is relatively affordable given its size, and comes with features like a timer setting, filter change indicator. It has two filters: a pre-filter to capture large particles like pet hair and lint, and a HEPA filter for smaller particles.
6. Dyson Pure Humidify + Cool
- Cleaning capacity: 400 square feet
- AHAM approved: No
- HEPA filter-equipped: Yes
This recently-released model is an air purifier, humidifier and fan, all in one. The Dyson Pure Humidify + Cool boasts a sleek design and plenty of bells and whistles, including a space heater, sleep timer, Wi-Fi connection, Alexa compatibility and nighttime mode. It also has a HEPA filter and is one of the only models that allows for oscillation. While pricier than other models, the Dyson may be best for shoppers looking for extra features.
7. Austin Air Healthmate Standard Air Purifier
- Cleaning capacity: 1500 square feet
- AHAM approved: No
- HEPA filter-equipped: Yes
This model offers a four-stage filter, which includes a HEPA filter, with a 60-square-foot radius. It uniquely has four filters, removing a different type of particle at each one. This includes a large particle pre-filter for dust and dander, a medium pre-filter for mold, a carbon filter for chemicals and gases and a HEPA filter for smaller particles. This model is much larger and heavier than others — it weighs 45 pounds — but includes rollers for easier transportation.
Tips for maintaining good air quality
Outside of buying an air purifier, there are some good home habits that you can adopt to help reduce the amount of air pollution in your space.
- If you can, open your windows for a period of time every day.
- Otherwise, make sure your heating or air conditioning system is running regularly to circulate air throughout your home, said McKeon.
- If you cook regularly, make use of your exhaust fans.
“With the focus on COVID-19, it is easy for existing health issues to fall out of focus,” McKeon added. “Triggers in the indoor environment have not gone away, so make sure you are reducing triggers where possible.”
