ASTM Bacterial filtration efficiency (BFE): Droplet sizes of 3.0 microns containing Staph. Aureus (average size 0.6-0.8 microns) are generated at face velocity of 28.3L/min and detected using six-stage viable particle cascade impactor. Measurement is taken after 2 minutes of aerosol exposure.
FDA Particle Filtration Efficiency (PFE): Polystyrene latex spheres 0.1micron are generated at 10^7-10^8 particles/m3 at face velocity of 0.5-25cm/sec and detected using an optical particle counter. Measurement is initial efficiency after 1-5 minutes.
NIOSH NaCl aerosol PFE: NaCl particles with effective size of 0.3micron are generated at face velocity 85L/min and detected using a light scattering photometer. Measurement is of maximum penetration (1-PFE). This is the most stringent of the three filtration tests meant to simulate penetration of submicron particles under heavy breathing conditions.
Pressure drop: Measures the air flow resistance of the mask and is an objective measure of breathability. The lower the value the more breathable the mask feels. Please note the different units because of different testing parameters (NIOSH PFE versus FDA PFE)
Fluid resistance: Reflects the mask’s ability to minimize the amount of fluid that could transfer from the outer layers through to the inner layer as the result of a splash or spray. ASTM specifies testing with synthetic blood at pressures of 80, 120, or 160 mm Hg to qualify for low (Level 1), medium (Level 2), or high (Level 3) fluid resistance.
Flame Spread: As hospitals contain sources of oxygen, heat, and fuel the ASTM F2100-11 standards include testing for flame resistance. Testing dictates that all masks must withstand exposure to a burning flame (within a specified distance) for three seconds.
ISO Certification: All medical face masks must be tested to an international standard (ISO 10993-5, 10) for skin sensitivity and cytotoxic tests to ensure that no materials are harmful to the wearer. Tests are conducted on materials used in construction of the mask which come in contact with the user's skin.
Fit Factor (FF): The result of a quantitative fit test, expressed as the challenge aerosol concentration outside the respirator divided by the challenge aerosol concentration that leaks inside the respirator.
