TSI Incorporated PORTACOUNT PRO+ 8038, Руководство по эксплуатации и обслуживанию

Страница: 91 / 107

85
Appendix C
Calculating Fit Factor
Fit factor is defined as the particle concentration outside the respirator
divided by the particle concentration inside the respirator.
Because ambient concentration can vary over time, the PortaCount
®
Pro Respirator Fit Tester calculates the fit factor by taking the average
of the ambient concentrations measured before and after the
respirator sample and then dividing by the concentration measured in
the respirator. This is why the first test cycle (exercise) is longer than
additional test cycles in Fit Test Mode. It is necessary to measure the
required additional ambient concentration sample before the first fit
factor can be calculated.
Both the ambient and respirator concentrations are determined by
integration. The integrated concentrations are determined by the total
number of particles counted during the sample periods.
Fit factor is actually calculated by:
R
A B
C
C C
FF
2


where: FF = fit factor
C
B
= particle concentration in the ambient sample before
the respirator sample
C
A
= particle concentration in the ambient sample after
the respirator sample
C
R
= particle concentration in the respirator sample.
If no particles are counted in the respirator sample, the PortaCount
Pro
fit tester automatically adds one particle. This prevents dividing
the ambient concentration by zero. At the end of a fit test, the overall
fit factor is calculated and displayed, based on the individual fit factors
for each test cycle.