Fit2fit Approved RPE Fit Testing Training Course

Quantitative Ambient Particle Counting Method (TSI Portacount)

The Ambient Particle Counting (APC) method compares the concentration of airborne particulates outside the mask and divides this by the number of particulates detected inside the mask to produce a ‘fit factor’.

The test is undertaken with a P3 filter (99.95% efficiency) fitted to the respirator, so any particles found inside the mask can be assumed to be the result of face seal leakage.

Source: TSI


Under the UK HSE protocol (INDG 479), half masks and filtering face pieces (disposable masks) require a minimum fit factor of 100 to pass, full-face masks need to have a fit factor of over 2000.

This method can be used to fit test all types of tight-fitting masks (e.g. FFPs, half-masks and full-face masks.


Dust2noise’s, one-day, APC RPE fit testing course is Fit2fit Approved and is always delivered by a Fit2fit Accredited Face Fit Provider and Chartered Occupational Hygienist.


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