Glossary of Terms

Explanation of  Commonly Used Terms


Filter Performance (PFE) – The filter is evaluated to measure the reduction in concentrations of specific aerosols in air that passes through the filter.

Total Inward Leakage (TIL) The amount of a specific aerosol that enters the tested respirator facepiece via both filter penetration and faceseal leakage, while a wearer performs a series of exercises in a test chamber.

Inward Leakage (IL)The amount of a specific aerosol that enters the tested respirator facepiece, while a wearer performs a normal breathing for 3 minutes in a test chamber. The test aerosol size (count median diameter) is about 0.5 micro meter.

Penetration of Filter Medium - The percentage of test aerosol penetrated through the filter material, e.g. melt blown.

Pressure Drop The resistance air is subjected to as it moves through a medium, such as a respirator filter.

Inhalation Resistance – The resistance of breathing in through a respirator.

Exhalation Resistance – The resistance of breathing out through a respirator.

Dead Space – The carbon dioxide content of the inhalation air.

Test Agent - The aerosol that is generated during the filter performance test.

Vision Field - The range of space that can be seen by the mask wearer with the head and eyeballs fixed.

Compatibility with Skin – Materials that may come into contact with the wearer’s skin shall not be known to be likely to cause irritation or any other adverse effect to health.


Bacterial Filtration Efficiency (BFE) – The percentage of infective agent that is retained by the surgical face mask, which is directly related to the amount of bacteria released through the mask into the air of the surgical theatre.

Splash Resistance – The resistance for penetration of potentially contaminated fluid splashes, such as ruptures in small arteries causing small sprays of blood.

Differential Pressure – The differential pressure of the medical face mask material by measuring the air exchange pressure through a measured surface area at a constant air flow rate.

Microbial Cleanliness – The Microbial Cleanliness test determines the total number of viable microorganisms on the face mask using an extraction method. The total viable aerobic microbial count and fungal enumeration is determined. Based on the weight of the mask, the results are reported as the total bioburden per gram tested for each mask..




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