What is PM2.5 BFE? July 14, 2020 23:48 Updated BFE stands for Bacterial Filtration Efficiency — meaning it can filter PM (particulate matter) of 2.5 microns! Related articles Will you make N95s? Does this mask have a nose guard? Do you need to replace the filters? How many washes does this last? Are you making sure people on the frontline get them first?