The quantitative fit test method (QNFT) measures the number of particles passing through a mask to assess the effectiveness of a specific piece of RPE on an individual.
This can be done either through measuring the ambient particle count (APC) as the challenge substance, or through measuring controlled negative pressure (CNP). In the UK, APC is the predominant QNFT method, using a PortaCount machine.
QNFT-APC uses a PortaCount machine to count the number of particles inside and outside the respirator mask while the subject undertakes a series of exercises, designed to mimic common strains on the seal of their mask. The difference between these two readings indicates the RPE’s Fit Factor detailing how much protection is given by the RPE.
Accurate, detailed and suitable for all mask types, QNFT is ideal for Fit Testing.