The width (zygomatic arches) and length (menton-sellion length) of the test subjects’ faces were measured (see Figure 1) using the digital caliper. The dimensions were measured twice for width, or three times if the measurement difference was greater than 2 mm. The average of the measured widths is recorded. The length of the face was measured twice, or three times if the measurement was greater than 3 mm. The average of the bizygomatic breadth and the menton-sellion length are identified with a panel number from the NIOSH panel (see Figure 1).
The masks tested were free of visual damage and randomly taken from the purchased lot of each subject model of filtering facepiece respirators (FFRs) and probed. (see Figure 3)
The filtration efficiency of each KN95 model was tested in advance. We drew three samples at random from each lot and tested them in accordance with 42 CFR 84 subpart K for N95. All samples tested above the minimum 95% standard.
Each subject was instructed how to correctly don the mask to achieve a good fit. Using a TSI PortaCount Plus® Model 8048 in the N95 companion mode, each subject was tested following the OSHA 29CFR1910.134 protocol, which consists of the following eight exercises:
- Normal breathing
- Deep breathing
- Head side to side
- Head up and down
- Talking
- Grimace
- Bending over
- Normal breathing
All subjects were standing throughout the test. The respirator fit capability (RFC) for each exercise and the overall respirator fit capability (RFC) result are provided in the detailed output of the program.