Homemade Masks

N95 masks designed for infection control are made of specialized filtration material engineered for that function ... Homemade masks can serve as a "prefilter" like what you see in your vacuum and HVAC systems and can potentially extend the life of an actual N95 mask, but they are not effective as infection control devices themselves

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/