Use a Box Fan with an Air Filter to Reduce Wildfire Smoke Indoors

 Learn a simple hack to improve your indoor air quality during wildfire season

Wildfires can reduce indoor air quality and can often cause health issues for people with lung and heart disease. Air purifying appliances work well to improve indoor air, but they can be rather pricey. Here is a simple, low cost hack combining a box fan and an air filter that will help you breathe easier indoors during a wildfire event.

Wildfire season typically runs from the end of the spring thaw through the beginning of the late-year wet season, depending on the part of the country you're considering. In the Southwest, the season typically starts in late May/early June. In the Northwest, it begins a little later. Areas in the eastern United States are more dependent on how wet the winter has been and whether tropical systems are dumping moisture throughout the summer and fall. The drier the season, the more likely it is wildfires will become an issue.

No matter what part of the country you live in, wildfires can wreak havoc on the air you breathe, both outside and inside. Your best bet is to stay inside an air-conditioned building with a high performance air filtration system, but that isn't always possible. According to the Puget Sound Clean Air Agency, if you find yourself in a natural disaster situation, such as a wildfire, with limited resources for purifying the air, combining an inexpensive box fan with a high-quality air filter could be a life-saving trick if you or someone you love suffers from heart or lung disease.

Step-by-Step Instructions for Creating a DIY Air Purifier

You'll need:



  1. Locate the back of the box fan – the side where the air will flows into the fan.
  2. Use your tape to attach the filter to the back of the box fan. Make sure the arrows on the sides of the air filter are pointing toward the fan. This will ensure the filter works properly as the air is moved from the back to the front of the fan.
  3. Seal the air leak gaps between the filter and fan as best you can.

That's it! It's really that easy! And less expensive than buying an air purifier appliance.

Tips for Getting the Best Results from Your Fan with an Air Filter

  • Your DIY Air Purifier will work best in an enclosed room. Make sure the doors and windows are closed so that you're not allowing additional smoke into the room.
  • Position the fan far enough away from the walls or furniture that might block the flow of air to the back of the fan.
  • Run the fan for at least 15 minutes to see the full filtration effect.
  • Only run the box fan with the air filter while people are in the room.
  • Buy the most efficient filter you can afford. MERV 13 air filters are proven to filter out smoke and fine particulates, so they will work perfectly for this purpose.
  • When the filter becomes discolored, it's time to change it. How long it will last depends on how much smoke and pollutants are in the air when you use it.

If you're interested in learning more about protecting your indoor air quality, check out the rest of our Helpful Tips.

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