This DIY Air Purifier Can Actually Help When Wildfire Smoke Spreads
We tested this popular social-media hack in the lab. Here's what you need to know before trying it at home.
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Wildfire smoke is again infiltrating parts of the U.S. and creating hazardous air conditions in the Northeast and Midwest. This mix of gas and fine particles can seep into your house or apartment through windows, doors, and cracks, and bring on respiratory irritation and shortness of breath. Consumer Reports’ rigorous testing has shown that air purifiers can be a useful tool to keep the air inside of your home safe.
The best air purifiers in our ratings are capable of clearing the air of harmful particles when set to high and low speeds—and they don’t make a huge racket while in operation. But as great as these purifying devices can be, many come at a hefty price. And when atmospheric conditions worsen abruptly, these machines often aren’t immediately available. In fact, one of the top-performing air purifiers in our ratings—the Coway Airmega ProX 3522F—is currently sold out.
“Air purifiers are in high demand and are continuously selling out in stores at a rapid pace,” says Marion Wilson-Spencer, CR’s market analyst for air purifiers.
To test a typical air purifier, our lab engineers inject smoke and dust particles into a sealed chamber and assesses how well each model removes particles between 0.1 and 1 micron. We used the same test for our DIY box-fan air purifier. Using a particle counter, we measured the change in particle concentration in the chamber as the fan ran for 15 minutes at its highest speed.
When we compared our DIY air purifier to those in our air-purifier ratings, our test results showed that—in terms of cleaning the air—it wouldn’t quite meet the threshold to be recommended, but it did fall in the middle of the pack and could help in a medium-sized room—one that’s about 200 to 250 square feet or smaller. It received marks near the top for dust removal at high speed and delivered an average performance in our smoke test—not bad if you’re in a pinch. “The result was surprising to me,” says Aminata Ndiaye, the test project leader for air purifiers. “It purified much better than I expected.”
You’ll probably get more impressive results if you use multiple filters on one box fan (known as the Corsi-Rosenthal box), but that can be cost-prohibitive given the price of filters. Regardless of what DIY direction you choose, our engineers recommend the following tips to maximize performance and safety:
- Start with a clean fan. Wipe down the blades and the box’s exterior, clearing away any dust.
- Make sure the arrows on the filter are pointing toward the fan. (The filters are directional.)
- Attach the filter to the backside of the fan. That way, air is pulled through the filter and not pushed against it.
- Tape the filter securely to the fan so that air doesn’t bypass it. And don’t skimp on tape around the corners.
- Place the fan on a stable surface and away from any obstructions.
- Don’t run your DIY air purifier unattended because the fan could overheat.
3 Great Air Purifiers for Wildfire Smoke
The USDA Climate Hubs report that wildfire season now lasts longer than ever before, the fires themselves are more frequent, and the size of the area damaged by these disasters has expanded. According to the Environmental Protection Agency, warmer springs and longer summer dry seasons, in addition to drier soils and vegetation, contribute to the current phenomenon.
Given how common these occurrences are, it may be worth investing in an air purifier that can run all day, unattended. After all, during wildfire events, we recommend leaving the air purifier on at all times.
Below are CR’s picks for the best air purifiers to handle wildfire smoke. For even more details on the 100-plus models, see our comprehensive air purifier ratings, where you can sort according to price, brand, and other criteria that matter to you most.
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