These HEPA (High Efficiency Particulate Air) filters are designed to work with Bullard's EVA Powered Air-Purifying Respirator (PAPR) systems including the Bullard EVA20LF2 Powered Air-Purifying Respirator w/ Loose-Fitting Facepiece (item # BL-EVA20LF2). These filters have an efficiency of 99.97% for dust, pollen, mold, bacteria and any airborne particles with a size of 0.3 microns (µm).