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Public Health Crafter’s Corner: 1-Minute DIY Filter Fan

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Welcome to the Public Health Crafter’s Corner: Wildfire Smoke Edition! Sadly, wildfire smoke is a near-annual event with the hotter, drier summers we’re getting (see Climate Changes Health). No amount of clever crafting can turn back the climate, but this simple D.I.Y. project can make the smoky days a little more bearable and safer.

Keep indoor air clean

When it gets smoky outside, try to stay inside as much as possible. This is true for everyone, but especially for children, people over 65, anyone with a health condition (like diabetes, heart disease, or asthma), and pregnant people.

It’s also important to keep the air inside as clean as possible so that your lungs can get a break. If you can, create a “clean room” as a refuge from pollution. Heat can be even more dangerous than pollution, so if it’s smoky and hot, you may need to open a window occasionally to cool it down–that’s when a “clean room” makes a huge difference.

One way to keep the air cleaner is by using an air purifier or air filter fan. And it turns out that you can easily make this at home in just 1 minute! Our friends at Puget Sound Clean Air Agency tested out DIY fan filters and found that they dramatically reduce fine particles and black carbon from the air!

How to make an air filter fan

DIY Air Filter YouTube screen capturePuget Sound Clean Air Agency shows how to make a DIY air filter fan by drilling holes into a fan and screwing brackets to hold a filter. It works great and looks tidy (definitely Martha Stewart would do it this way), but frankly, when I see that drilling is involved, I’m just not going to do it. But my local hardware store gave me a great tip to make it SUPER easy (and I got approval from my colleagues in our Environmental Health Services division).

What you’ll need:

  • 20″ x 20″ electric box fan
  • 20″ x 20″ MERV 13 or FPR 10 air filter (MERV 13 or FPR 10 are the ratings for filters that can filter smoke particles)
  • One 48″ bungee cord (or multiple bungee cords that can link together to make it 48″ un-stretched*)

Here’s what you do:

  1. Find the arrows on the outside edge of the filter box. Find the backside of the box fan.
  2. Press the filter against the backside of the box fan with the arrows pointing towards the fan.
  3. Wrap bungee cord around the fan and the filter and hook the two ends together so that the filter is secured to the fan*.

And that’s it! You can also use duct tape instead of a bungee cord.

*Public health tip from our staff: make sure the bungee cord is long enough, or use multiple bungee cords, so that the cord doesn’t stretch too tightly, recoil, and snap you in the face! We public health professionals do think of all the hazard angles.

Tips for using your DIY filter fan

  • Run the fan for at least 15 minutes to clean the air.
  • Close the windows and doors while the fan is in use so that polluted air doesn’t re-enter the room.
  • Make sure the filter fan doesn’t overheat (it has to work hard to pull air through the filter). Turn it off every 30 minutes or so to rest for about 15 minutes. Don’t leave it running while you’re out of the house or sleeping.
  • Use the filter fan in the room you spend the most time in, positioned toward the middle of the room.
  • Move the filter fan to your bedroom for at least 15 minutes before you go to bed so that you can clean the air in the space where you sleep.

Take it to the next level

If you want to maximize the air filtering, here are a couple of options (also easy!):

  • Seal the edges between the fan and the filter with extra-strength packing tape. This prevents unfiltered air from seeping through the fan around the edges.
  • Make an air filtration “cube” using 5 MERV-13 filters, a box fan, and duct tape. Some legit crafters on This Old House show you how in this video.

We have more information about how you can be prepared for wildfire smoke season: kingcounty.gov/wildfiresmoke


Meredith Li-VollmerContributor Meredith Li-Vollmer is a risk communications specialist at Public Health—Seattle & King County

Originally published in Public Health Insider on July 16, 2021.

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