How to keep indoor air clean on smoky days

On most days, our homes provide a refuge, sheltering us from the elements. But, what our homes are not so good at is maintaining clean indoor air, especially during wildfire smoke events.

During the 2017 wildfire season, Missoula Public Health found that, in facilities and homes without air filtration systems, their indoor air quality mirrored outdoor air quality. Our boundaries are more permeable than we might think.

Tiny particles are the problem

Wildfires burn wood and other organic material, creating smoke that contains gases and fine particles. These fine particles are smaller than ten microns; for comparison, diameter of a human hair is forty to fifty microns.  And the particles are particularly bad for human health. They can be breathed into the lungs, where they can act as respiratory tract irritants, and smaller particles can even penetrate deeper into the bloodstream and cause widespread inflammation. Children, adults sixty-five and older, pregnant people and people with lung or heart conditions are particularly vulnerable.

Make your house ‘tight’

We have some tips to keep these tiny (yet mighty) particulates out of your home.

One of the main ways that smoke can enter and leave a building during wildfire smoke events is through windows and doors. Keep windows and doors shut as much as possible to prevent smoke from entering the home.

You might still have gaps in windows and doors that allow smoke to enter, especially if you live in an older building. If you are sensitive to smoke, it is best to close these gaps by applying weather stripping around doors and windows. Weather stripping include things such as v-strips, foam tape, and door sweeps, all of which you can buy at your local hardware store.

Note: Heat can be another serious health hazard, so if your home becomes too hot, it’s better to open up a window and cool the home down, even if it lets in some smoke.

If you don’t have air conditioning, create a ‘clean room’

Most people in our region don’t have air conditioning at home and may need to open up windows for short amounts of time if it becomes unbearably hot inside. If you can’t keep the smoke entirely out of the home, make a “clean room” so that you have place inside the home with cleaner air. It is best to choose the room that is most heavily occupied throughout the day and that has few doors and windows.

What you will need to make a “clean room:”

Avoid other sources of air pollution

To keep the room’s indoor air clean, avoid introducing other sources of air pollution. Avoid activities that would create fine particles indoors, including:

  • Burning candles or incense
  • Smoking cigarettes
  • Spraying aerosol products
  • Using gas stoves, wood-burning stoves, or fireplaces
  • Frying or broiling food
  • Vacuuming

Clean the air

The most cost-effective way to clean your indoor air is to make a Do-It-Yourself (DIY) air cleaner using a box fan and a filter. Check out our DIY fan filter tips or Puget Sound Clean Air Agency’s DIY air filter website for step-by-step instructions.

The drawback of the DIY air cleaner is that, unlike the portable air filtration unit, it is not designed for continuous use. This means you’ll need to turn it off when you’re out of the house or sleeping. However, you can move the DIY air cleaner into the bedroom for 15 minutes before you go to bed so that you are able to filter out the space before you sleep.

Portable air cleaners rapidly clean the indoor space by pushing the air through a filter multiple times per hour. Leave it running continuously, 24 hours a day, 7 days per week during wildfire smoke events to ensure that the air stays clean.

For a single room setting, these portable air cleaners typically range from $200 to $300. Wirecutter has a review of some of the top portable air cleaners. Make sure to take into account the cost of the replacement filters, in addition to the unit itself, because these can often be a hidden cost. Also, we recommend sticking to the mechanical air cleaners (described above) versus the electronic ones, which often produce ozone as a byproduct.

For all types of portable air cleaners, change the filter frequently during periods of high wildfire smoke when there is a lot of infiltration. As a general rule of thumb, you’ll want to change the filter if it visibly starts to darken.

Ezekiel shows off a portable air cleaner t in his role as Clean Air Superhero. All portable air cleaners are ranked based on the “MERV” rating system from 1 through 20, which measures how efficient the filter is at capturing particulates. Any portable air filtration unit with a MERV 13 or higher will be effective at filtering out problematic particulate matter.

Clean out the room if air quality improves

The last part of maintaining a clean room is taking advantage of periods of improved air quality by opening windows and cleaning surfaces. Check the outdoor air quality before taking any of these steps though, because sometimes it can look clear outside, even though the outdoor air still has high concentrations of particulate matter. Visit EPA’s AirNow or Puget Sound Clean Air Agency’s website for up-to-date information on air quality in your area.

In addition to opening your windows, clean out any ash that has accumulated with a wet mop and damp rag. With vacuums, brooms, and feather dusters, you run the risk of stirring particulate matter back up into the air.

If you have air conditioning

If have central heating/cooling in your home, replace the filter with a higher efficiency filter (MERV 13 or higher) if it does not already have one. You may need to consult with a technician or the manufacturer of your system to confirm which of the high efficiency filters will work with your central air system. You’ll also want to switch the air condition to the “recirculate” mode so it doesn’t bring in outside air.

For more information

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Originally posted on September 9, 2020.