As wildfires become more common in various parts of the country, the smoke carries hundreds of miles. That smoke can also enter homes, schools and businesses. Protecting indoor air with HEPA filters can be expensive, so a team from the University of California Davis designed a do-it-yourself box filter that can be built for a fraction of a commercial HEPA filter. It uses four air filters common in household air systems, a cardboard base and a box fan to draw air through the filters and toward the ceiling. In tests on the UC Davis campus, the box filter performed as well or better than comparable HEPA filters because much more air passes through the box filter. The DIY project was presented to the American Chemical Society’s Spring Digital Meeting.