ISRP 1999 abstract
National Institute for
Occupational Safety and Health
|Comparison of the Companion and Modified PortaCountTM Methods for Fit Testing N95 Respirators||
In 1995, the National Institute for Occupational Safety and Health (NIOSH) revised the particulate respirator performance regulations contained in Title 42 Code of Federal Regulations, Part 84. Soon after questions arouse regarding whether N95 respirators (one of the new classes of particulate respirators) could be quantitatively fit tested. In response, NIOSH and TSI Incorporated researchers developed a method for fit testing N95 filtering‑facepiece respirators using the PortaCount PlusTM. The PortaCount PlusTM fit test was designed to measure fit factors (i.e., face seal leakage only). Due to some N95 filter media having significant penetration of ambient particles, the PortaCount PlusTM when used with a N95 respirator may not measure just face seal leakage but total penetration (i.e., filter penetration and face seal leakage). Total penetration was converted to face seal leakage by subtracting out filter penetration. A filter ratio test clamp was developed to measure filter penetration with the PortaCount PlusTM. TSI also developed a new accessory (the N95‑COMPANIONTM for the PortaCount PlusTM) to fit test N95 respirators.
The purpose of this study was to determine how well the fit factors from these two methods correlate. The facepiece fit of each respirator model was measured on a panel of subjects with varying face sizes. A "standard" PortaCount PlusTM test was conducted for each subject/respirator combination. Immediately after the "standard" PortaCount PlusTM test, a fit test for each subject/respirator combination was conducted using the N95‑COMPANIONTM in conjunction with the PortaCount PlusTM without the respirator being redone. After the N95‑COMPANIONTM test, filter penetration was measured on each respirator using the PortaCount PlusTM with the clamp, and an adjusted fit factor computed. The results of analysis of variance indicated that the geometric mean of the N95‑Companion TM fit factor (49) was not significantly different from the geometric mean of the adjusted fit factor (35).