Wildfire smoke is here to stay. Here’s how to clean the air inside your home

The wildfires that spread across much of the western United States this summer, spreading smoke hundreds of miles, continue to pose a serious health threat to millions of people.

More are expected this fall. That’s a major health risk because microscopic particles in the smoke from forest fires, carried by the wind, can penetrate deep into your lungs and enter your bloodstream. One study linked wildfire smoke exposure to a twofold increase in asthma and a 40% increase in strokes and heart attacks. Other research linked smoke to hospitalizations, ER visits and premature deaths.

The standard advice is to stay indoors when there is a lot of smoke in the air. But the smoke can get into your house or apartment. So you may want to consider investing in equipment to clean the air in your home, especially now that climate change is likely to continue to escalate the size and intensity of fires.

“I think we have enough fires now that people should see this as something they want to buy,” said Deborah Bennett, a professor of public health at the University of California-Davis. “Even if they only turn it on during the fires, there will be plenty of times when they will turn it on.”

There are many options for cleaning the air in your home, depending on your circumstances and your budget.

If you have an HVAC system, it probably recirculates the air that is inside the house instead of drawing in air from outside. However, if you have an air conditioner with a “fresh air” system that brings outside air in, you should turn off the fresh air mode on smoke-filled days. If you don’t know how, seek professional advice.

And shut all doors and windows; otherwise your efforts will be in vain.

You can convert your HVAC unit or furnace into a better air cleaning system by installing a higher efficiency filter that can capture a lot of the small smoke particles, although it won’t get it 100%.

To cope with smoke from wildfires, many public health and air quality experts recommend a so-called MERV 13 filter. MERV, or “minimum efficiency reporting value,” is a scale from 1 to 20 that rates a filter’s ability to trap particulates. MERV 1 is the lowest rating, indicating the least impact on air quality, while filters rated at MERV 17 or higher are used in operating theaters and hospital cleanrooms.

You can purchase MERV 13 filters from major retailers such as Costco, the Home Depot, and Lowe’s, or online from multiple suppliers. A MERV 13 should cost about $20, or considerably less if you buy packs of it.

Before installing a new filter, check with an HVAC professional to make sure your system can handle it. The more efficient the filter, the more it reduces airflow, decreasing the cooling capacity of an air conditioner and requiring more energy to run the heater.

If you don’t have central air, or you do have one and you want to increase your system’s ability to purify the air, consider purchasing a portable air purifier with a highly efficient particulate air or HEPA filter, which is nearly can remove all particles of the small size found in smoke.

You can put it in the room you use most during the day and move it to your bedroom at night. If the smoke gets really bad, put it in the room of your choice and stay there as much as possible.

“If you have a properly sized air purifier with a true HEPA filter and you put it in a room and close the doors and windows, you’ll have clean air very quickly,” said Sarah Coefield, an air quality specialist at the Missoula City Center. County Health Department in Montana, which has had its share of smoke from wildfires in recent years.

If you have children, or if you share the house with other people, you should ideally have one air purifier for each bedroom. Alternatively, it may be necessary to put everyone in one room overnight during a smoking emergency.

Portable HEPA air purifiers cost anywhere from less than $100 to over $1,000, depending in part on how many square feet they can effectively clean. To clean a room, you can get a perfectly good one for under $200.

Public health experts warn that you should avoid devices that are sold as air purifiers, but that emit ozone, the main component of smog. The Air Resources Board also publishes a list of devices that release ozone.

Gina Spadafori, of West Sacramento, California, has both a central HVAC system with an extra thick filter and a portable HEPA air purifier that she keeps in her bedroom. Spadafori, 63, has severe asthma and has long been concerned about the air quality in her home.

Over the years, she has endured countless days of dangerous wildfire smoke, and that has changed the way she uses her HVAC. “I probably use the fan-only setting more than in the past to filter the air instead of heating or cooling it,” she says.

On bad air days, she turns on the portable air purifier an hour before going to bed and closes the door so it “super cleans the air” and gets a good night’s sleep. “It’s just kind of a second line of defense,” she says.

There’s a cheaper option: Make your own air purifier by attaching a high-efficiency filter to an electric cabinet fan. You can get a suitable fan for about $30 and the filters for about $20 – or cheaper in bulk.

The website montanawildfiresmoke.org publishes a guide to building such a thing. The Environmental Protection Agency has an FAQ on box fan air purifiers with instructions on how to build them.

The EPA recommends using only box fans built in 2012 or later because earlier models can overheat and cause fires.

Lab tests have clearly shown that such DIY devices are safe, although they can heat up the room and produce more noise than a portable HEPA cleaner, according to the EPA.

For those who can’t even afford to make an air purifier out of a home fan, nonprofits and local government agencies have provided help. People who don’t have a lot of money are likely to live in older, leakier homes that have more smoke coming in. They are also more likely to suffer from chronic diseases and thus need more clean air – but can afford it less.

Climate Smart Missoula, a Montana nonprofit, has distributed about 500 air purifiers to low-income and home-bound people in recent years, said Amy Cilimburg, its executive director.

In California, the Bay Area Air Quality Management District supplies 3,000 air-filtration equipment to low-income people with respiratory illnesses in nine counties. The American Lung Association has also donated air purifiers to those in need.

But these efforts are small compared to the yawning need, said Cilimburg, who believes federal and state governments, hospitals and insurers should step in. She envisions a day when medical staff in a clinic will tell a patient, “‘Oh, look, given x, y, or z, just take one of these HEPA filters home with you.’ ”

This column was produced by Kaiser Health News, a non-profit health news service. It is an editorially independent program of the Kaiser Family Foundation, which is not affiliated with Kaiser Permanente.

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