Wildfire Particles Can Get Into Your House And Make You Cough. Here’s How To Keep Them Out.

When California wildfire season started up last month, Liya Rechtman began smelling smoke in her apartment.

“Like the end of a campfire, but all the time,” she said.

The 28-year-old and her partner live in an old midtown building, and it wasn’t keeping the bad air out. They bought two different standalone air filters, which she said helped. And they asked their landlord to add insulation to the door.

“We’d been putting wet towels on the bottom of our door, as if we were in college and trying to prevent pot smoke from getting in and out of our dorm room,” she said. “It just felt very bizarre … at the base of every window you could see ash collecting.”

With unhealthy air expected to linger, Sacramento residents are receiving consistent advice from public health officials: stay inside. Experts warn the particles from wildfire smoke — which are about one-twentieth the width of a strand of human hair — can penetrate deep into the respiratory system and cause problems, especially for people with pre-existing conditions.

But there are major challenges to keeping indoor air breathable. When too much smoke comes in and renders filtration systems ineffective, people can experience coughing, irritation and other symptoms, said Dr. Justin Chatten-Brown, emergency department medical director at Woodland Healthcare.

“Air quality can be just as bad indoors as out of doors, especially for at-risk populations who may not have access to air conditioning and rely on self-ventilation and open doors to maintain a cooler environment,” he said.

Deborah Bennett, a professor of Public Health Sciences at UC Davis, says how well you can prevent outdoor air from seeping in depends a lot on where you live. 

“If you have more modern construction and a more tightly built house, you’re going to have greater filtration through the building shell,” Bennett said. “If you’re in an older home that might leak, that you can tell air is coming in around the edges, that’s going to bring in more particulate matter.”

Chris Chavez, deputy policy director for the advocacy group Coalition for Clean Air, says air filters and HVAC systems are not a given in low-income areas.

“Folks who live in those communities tend to not have the same access to options, so it will be difficult,” he said. “And from a policy point of view, policymakers need to consider how to invest in communities so that lower-income residents, communities of color do have access to options to protect their lungs.”

For now, here are some things you can do to try to keep particulate matter out of the air in your home.

Choose the right filter for your space

There are two primary ways to filter a space — using a central air system filter, or a high-efficiency portable air cleaner. You can find a detailed breakdown of each option and how it helps with wildfire smoke here.

Bennett says the No. 1 mistake people make when it comes to air filtration is choosing an air filter that’s too small for their home. She says an air filter that’s appropriately sized can reduce the concentration of unhealthy particles by 50% to 75%.

“If they have just a small air filter that’s meant for a room, and they’re trying to use that to try to filter their whole house, you're not going to see those kinds of reductions because it’s not running enough air through the air filter,” she said.

She recommends checking the packaging on filters to try to find a good match.

“If you have a small air filter, put that in the room where you are in, that you and your family are in and shut the door, so it’s only trying to filter the air in that room,” Bennett said. “You’re going to be much more successful in lowering the particulate matter if you’re trying to lower it in a smaller space.”

In terms of purchasing an air filter, the California Air Resources Board has a list of certified products they recommend during wildfire season. They warn that some indoor air cleaners actually emit large amounts of ozone, the main component of smog. The board does not recommend running swamp coolers or whole-house fans.

Experts say it’s a good idea to keep windows and doors closed when the air is unhealthy. Bennett recommends using weather stripping and other strategies to keep outside air from entering your home. 

Use Your AC Properly

If you have an HVAC system, the California Air Resources Board recommends running your air conditioning on “recirculate” mode with a new filter. 

“If you have a central ducted air conditioning and heating system, be sure to set the system to “on” to ensure air is being filtered constantly, rather than “auto,” which runs the system intermittently,” the agency wrote in their guide to indoor air during wildfires.

When you’re choosing a filter for your HVAC system, it’s important to look at the MERV, or Minimum Efficiency Reporting Value rating. The higher the rating is, the more particles are captured as air passes through the filter. Experts generally recommend filters with MERV ratings of 13 or higher.

Limit indoor pollution

There are things we do inside our house that can make the air quality worse, too. Here’s a list of things you may want to avoid doing if you’re becoming irritated by bad air:

• Burning candles
• Using gas stoves
• Smoking inside
• Vacuuming

The California Air Resources Board recommends using a damp cloth or mop to trap settled dust and particles

Sarah Mizes-Tan contributed reporting.