Q&A – What is the Delta P and BFE of Berkshire’s face masks?

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Q&A – What is the Delta P and BFE of Berkshire’s face masks?

The Differential Pressure (DP) is a test that measures how easily air is passed from one side of the mask to the other. This indicates how easily the wearer can breathe through the mask, and is in indicated by Delta P. Higher DP indicates air is more difficult to push through. This could result in a “blow-by” effect (escape of air, and contamination from the sides of an improperly work mask), or even incorrect use by the wearer. While not as comfortable, the higher Delta P results in better filtration.

Choice® Face Mask Part Number

Differential Pressure (mm H20/cm)





Above 5.0


4.0 to 5.0

Very Warm

3.0 to 4.0


2.0 to 3.0


1.0 to 2.0

Very Cool

The Bacterial Filtration Efficiency (BFE) tests face mask filtration material. The results are expressed in the % of bacteria larger than 3.0µm (microns) that are being filtered by the face mask. How small is a micron? 

Choice® Face Mask Part Number

Bacterial Filtration Efficiency (%) 3.0µm



Click here to view an infographic explaining the proper way to wear a face mask.

Cleanroom Or A Store – How To Wear A Face Mask Correctly

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