New research from Virginia Tech University finds that coffee filters not only keep oils from making their way to the cup during brewing but may also block the coronavirus.

As reported by KGW in Portland, researchers from VT examined the efficacy of paper coffee in blocking COVID-19 sized particles. For the study, researchers compared particle transmission when using one, two, and three filters. They found that while one and two filters didn’t have much of an effect, using three filters had a beneficial outcome. As explained by Portland State University’s Dr. Richard Corsi, an air quality expert:

If you put three coffee filters layered on top of each other, you can get on the order of 50, 60 or even 70 percent removal efficiency for particles the size that we care about for the coronavirus.

Dr. Corsi notes that, while effective, using three coffee filters comes with a cost: the impromptu mask is difficult to breath with. The same filter keeping out coronavirus-sized particles also impedes oxygen flow.