ASTM F2299 Particulate Filtration Efficiency (PFE) Measures the initial particulate filtration efficiency of materials used in medical facemasks. Aerosol: Latex spheres (PSL) (0.1 µm typically). Face Velocity (i.e., flow rate/test area): 0.5 to 25 cm/s. ~11 liters per minute used at Kinectrics. Optical particle counter used to determine upstream and downstream concentrations.