Do you really need an air purifier?

Boston Globe

a day ago

What to look for
Air purifiers vary in size, from sleek desktop models to larger units that resemble portable heaters. But they all work in pretty much the same way.
The machine pulls in air, which then passes through a filter. 'It's the same material that's in masks,' said Linsey C. Marr, an environmental engineer at Virginia Tech. 'The filters have very small fibers and small spaces in between them, so the particles have a tough time getting through that, and they end up getting trapped.'
The most effective filters have what's called high-efficiency particulate air certification. Better known as HEPA filters, they can capture up to 99.97% of common particle pollutants including mold, dust, pet dander, pollen and smoke.
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Air purifiers are also rated by their clean air delivery rate, or CADR, which is based on how much air they can move per minute. 'The higher the CADR, the more particles the air cleaner can filter and the larger the area it can serve,' according to an air purifier guide from the Environmental Protection Agency.
Some models also come with carbon filters. 'That's going to absorb any gases out of the air, like benzene or other VOCs from everyday products,' said Joseph G. Allen, director of the Healthy Buildings Program at Harvard University. He was referring to volatile organic compounds, a class of common and often dangerous gases that can build up indoors because of emissions from gas stoves and fumes from paint, household cleaners and thousands of other products.
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Gases aren't particulate matter, so they can't be captured by a HEPA filter. 'The two filters, working in tandem, do a really good job,' Allen said of air purifiers that come with both HEPA and carbon filters.
All about pollution
Dr. Stephanie Lovinsky-Desir, chief of pediatric pulmonology at the Columbia University Irving Medical Center, said that people who lived 'near sources of pollution such as major roadways, industrial sources or wildfires' should consider purchasing an air purifier, as should people with chronic respiratory conditions.
That applies especially to children. 'Children who live in communities that are exposed to lots of traffic-related air pollution are at risk for having asthma and having worse symptoms and outcomes from asthma,' Lovinsky-Desir said.
A 2020 study by Korean researchers looked at how children with asthma responded to particulate matter in the air they breathed. The study concluded that 'air purifiers are beneficial to asthma patients.'
Keep in mind that, as Allen noted, not all pollution comes from the outside. Everyday cooking also emits a host of pollutants, including oil droplets that can become carriers for carcinogens and a stew of other dangerous particulates.
'The highest particle concentrations we ever see in my house are when we're cooking,' Marr said. 'Even if you cook your food without burning it, it still generates a lot of particles, if you're sauteing something on the stove, for example.'
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Sneezing and wheezing
As anyone who has seasonal allergies knows, pollen from trees always seems to find its way inside. And the problem is only getting worse, Lovinsky-Desir said, because of rising global temperatures. 'With warmer climates, we're seeing earlier pollen exposure, longer pollen seasons,' she said in an interview.
Air purifiers can significantly reduce medication requirements for people with allergies, the 2020 Korean study found.
Breathing smoke
Climate change is leading to more intense and more frequent wildfires.
The pollution from those fires can travel for hundreds of miles, as we've seen this month, with smoke from blazes in the Canadian prairies drifting to Eastern Canada and the Northeastern United States.
Smoke 'can be irritating to the airways of anybody, even people who are traditionally less sensitive because they don't have underlying conditions,' Lovinsky-Desir said.
Katherine Pruitt, a senior policy director at the American Lung Association, suggested that people in wildfire danger zones set up a 'clean room' with air purifiers in preparation for the possibility of smoky air rife with pollutants.
Not 'the first line of defense'
According to Pruitt, air purifiers 'should not be the first line of defense for clean indoor air' for most people, especially since their cost can be prohibitive.
As a first step, she advises people concerned about indoor air quality to use a vacuum cleaner with a HEPA filter, to wash bedding often to get rid of dust mites and to make sure there's no mold in their homes.
'We don't want to sensationalize and drive people to think they have to make a purchase without taking some other steps first,' Pruitt said in an interview.
She also suggested making sure that your stovetop vent hood is blowing air outside, not merely recirculating it. Cooking on a back burner, Pruitt added, makes it more likely that nasty particles will be sucked up and blown out of your kitchen.
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Nevertheless, air purifiers can be especially helpful to people with asthma and allergies, especially children, and also to the estimated 115 million Americans who live in areas prone to wildfires. 'Without a doubt, people who suffer from allergies will find benefits,' Allen said.
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