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 Do you need to replace the filters? How many washes does this last? Is the FIONx Protective Mask an N95? Does this mask have a nose guard? Are you making sure people on the frontline get them first?