With wildfires and dust storms seeming to happen more often, many are looking into ways to make the air in their homes safer to breathe.

A do-it-yourself (DIY) air filter is an affordable air-cleaning device that typically uses a standard household fan paired with a filter medium to remove particulate matter (PM) from indoor air. Such filters have gained attention during events such as wildfires and sandstorms, when commercial air purifiers may be prohibitively expensive or unavailable. This setup draws air through the filter before it reaches the fan, purifying the air as it passes through. [1]

Register Vent Filter Implementation

Rather than having a filter sitting in the room, some instead buy vent filters so that the air from heaters or AC's is filtered. [2] These sometimes have magnets or stick-on velcro to attach the filters to the vent covers.

Circular Fan Implementation

Rather than furnace filters, some people propose using washable fabric filters mounted to a fan. These filters may be reusable, though typically offer lower filtration efficiency than MERV-rated filters. The performance depends strongly on the fabric's structure and fiber composition, but layering fabrics can filter between 12%-96% of particles. [3] [4]

A better option for circular fans is to get a filter shroud with a filter rating. The shroud covers the sides, and in doing so ensures that more air is pulled through the filter, instead of around it.

Box-Fan Implementation

1. Use a box fan with safety certification and thermal protection.
2. Attach a MERV-13 (or higher) furnace filter to the intake side of the fan, ensuring the arrow on the filter aligns with the airflow direction.
3. Consider using multiple filters (e.g., four filters in a cube) to increase surface area and reduce pressure drop.
4. Monitor and replace filters when they become dirty or loaded; replacement frequency depends on air quality and particulate loading.

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