P
ORTA
C
OUNT
®
Plus Model 8020 Technical Addendum
revised 7-27-2001
TSI Incorporated, St. Paul, Minnesota, USA
23
Copyright © 2001 all rights reserved
N95-Companion Model 8095
The N95-Companion is an accessory for the
PortaCount Plus that permits the PortaCount to
perform quantitative fit testing on low efficiency
disposable respirators such as class-95 (USA) and
class-P1/P2 (other countries). The N95-
Companion is essentially an electrostatic particle
classifier (a.k.a. Differential Mobility Analyzer or
DMA) that strips off all particle sizes above and
below the target particle size of approximately
0.04 micrometers. The target particle size is
fixed and cannot be adjusted. Refer to the
N95-
Companion Operation and Service Manual
(TSI
part no. 1980308) for operation and maintenance
instruction. Visit
To operate with the N95-Companion the
PortaCount Plus must have the revision A
modifications. The tag on the bottom of the
PortaCount Plus will show MODEL 8020A if it
is "N95-Companion ready." Revision A
modifications can be added to older PortaCounts
via factory service.
N95-Companion Theory of Operation
The fundamental assumption made when fit testing with the PortaCount is that any
particles sampled from inside the respirator must have entered through a leak since they
cannot pass through the filter. This assumption is always true for high efficiency filters,
but fails for low efficiency filters. There are enough particle passing through low
efficiency media to bias the fit test and cause very low fit factors even when the face seal
is perfect. The PortaCount does not know the difference between a particle that entered
via a face seal leak and one that passed through the filter media.
Sampling Pendant
N95-COMPANION
PORTACOUNT
VALVE
Ambient
Sample
Mask
Sample
Exhaust
