California is still reeling from devastating wildfires that have tragically claimed many lives and thousands of homes. As the fires continue to burn, the smoke has collected throughout the San Joaquin basin, slowly feeding its way out over the San Francisco Bay Area. In turn, that area is currently experiencing air quality that is the worst on the planet.

It’s really awful — many of the residents and visitors are now wearing N95 respirators outdoors, which have become hard to find as stores are selling out due to the haze. Schools are closed and people are strongly urged to stay inside. The smog is so thick it’s obscuring visibility even a half mile away.

If you are in the area, you may find an air filtration system will help keep your interior space clear. These can be hard to find quickly with the conditions, however. But a quick solution, as posted by the University of Michigan’s Medical Center, is to create your own filter using a box fan and a standard HEPA filter, both readily available in most hardware stores and costing about $25 for everything. You might even have these items in your garage already.

The Wirecutter reports that this solution is effective — although not to the degree of a dedicated machine.

Please stay safe.