N95 Airflow resistance filtration efficiency and strap integrity testing after exposure to ozone 450 ppm at 75%–90% humidity for 2 hours per cycle
| Respirator type | Number of ozone treatment cycles | Mean filtration efficiency±SEM (%) (range) | Mean filter resistance±SEM (mmH2O) (range) | Top strap mean force ±SEM (N) (range) | Bottom strap mean force ±SEM (N) (range) | Overall mannequin fit factor mean ±SEM (mFFO) (range) |
| 3M 1870 N95 Respirator | 0 (controls, n=5) | 99.42 ±0.43 (99.57–99.87) | 8.53 ±0.18 (8.2–8.6) | 1.708 ±0.083 (1.581–1.865) | 1.753 ±0.028 (1.703–1.799) | 172.3 ±10.8 (161-194) |
| 5 (n=5) | 99.83 ±0.04 (99.72–99.93) | 8.64 ±0.45 (7.8–10.3) | 1.704±0.222 (1.263–1.978) | 1.660±0.175 (1.313–1.876) | 186.7±3.3 (180-190) |
N95 respirators were exposed to ozone at Ozone Solutions and filtration and strap integrity tests were performed at the CDC. Filtration efficiency testing was performed on five respirators. Filtration efficiency tests used the TSI model 8130A per protocol in NIOSH N95, 42 CFR Part 84 (Respiratory Protective Devices) (TSI) using 0.26 µm aerosolised sodium chloride under a flow rate of 85 L/min. Quantitative fit testing was performed on three respirators using a mannequin fit factor (mFFO) with Statis Advanced Headform (Hanson Robotics) following the protocol as defined by OSHA 1910.134(f)(7) where tight-filling facepieces undergo a pass/fail test to assess for change in fit performance associated with disinfection of respirators. mFFO scores range from 0 to 200 and are quantitative assessments of fit that can be replicated with other quantitative fit-testing devices. Scores greater than 100 are considered to have passed this quantitative fit testing, that is, no change in fit performance is detected. Tests were performed on stationary mannequin headforms simulating normal and deep breathing.9–11