TSI Incorporated PORTACOUNT PRO+ 8038, Operation And Service Manual

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Appendix E
Timing in Fit Test Mode
Test Sequence
When performing a fit test, PortaCount
®
Pro Respirator Fit Tester
automatically samples both the ambient air and the particles inside
the respirator. An internal switching valve automatically switches
between the two sampling ports. In each test cycle, (exercise) both an
ambient sample and a respirator sample are taken. Also, time is
allowed for purging of the sensor between each of the samples.
The PortaCount Pro
fit tester uses the ambient sample taken before
and after each exercise to compute the fit factor. The two ambient
particle concentrations are averaged together and then divided by the
mask particle concentration to yield the fit factor for that exercise.
Averaging the before and after ambient particle concentrations is
done to offset any ambient particle concentration drift that may have
occurred during the mask sample.
C a u t i o n
Do not lengthen the Twin Tube Assembly more than a
few inches unless the mask sample purge time has also
been extended accordingly. Insufficient purging between
mask and ambient samples will result in unrealistically
low fit factors. Shortening the Twin Tube Assembly is
never a problem.