Table III.
Summary of results following N95 FFR decontamination for each outcome of interest and chemical disinfectant type
| Disinfectant | Aerosol penetration | Airflow resistance | Viral/bacterial load | Fit | Physical traits | Potential health risks |
|---|---|---|---|---|---|---|
| Sodium hypochlorite | No change in aerosol penetration, aerosol penetration <5% maintained (N = 4) | No change in airflow resistance, NIOSH standards maintained (N = 3) | Log10 reduction in viral levels of 0.66 ± 0.47 to 4.37 ± 0.4 depending on concentration used (N = 2) | Not assessed | Tarnished metallic nosepieces (N = 4) | Potential for low-level chlorine exposure when FFR is rehydrated during respiration (N = 1) |
| Aerosol penetration exceeded 5% for particles >63 nm (N = 1)a | 0% relative survival of bacteria (N = 1) | Oxidized staples (N = 2) | ||||
| Mean reduction in bacteria levels >99% (N = 1) | Yellowing of nose pads (N = 1) | |||||
| Bleeding of lettering (N = 1) | ||||||
| Stiffening of filter media and elastic straps (N = 1) | ||||||
| Dissolved nose pad (50%) (N = 1) | ||||||
| Bleach odour following treatment (N = 3) | ||||||
| Liquid H2O2 | No change in aerosol penetration, aerosol penetration <5% maintained (N = 2) | No change in airflow resistance, NIOSH standards maintained (N = 1) | Not assessed | Not assessed | Oxidized staples (N = 1) | Did not deposit significant quantities of toxic residues on the FFRs (N = 1) |
| Slight fading of the label lettering (N = 1) | ||||||
| No changes in odour (N = 1) | ||||||
| Vaporized H2O2 | No change in aerosol penetration, aerosol penetration <5% maintained following one (N = 2) and three decontamination cycles (N = 1) | No change in airflow resistance, NIOSH standards maintained (N = 2) | No viable virus, or virus or bacteriophage below detectable assay limit (N = 4) | Fit factor >100 achieved following 1, 3, 5, 10 cycles with the VHP ARD system, but only following one cycle using the Sterrad 100NX (N = 1)b | Slight tarnishing of metallic nosebands (N = 2) | Did not deposit significant quantities of toxic residues on the FFRs (N = 2) |
| Aerosol penetration exceeded 5% for four out of six FFR following three decontamination cycles (N = 1) | Fit factor >100 achieved following 3 × 2 h wear + decontamination cycles (N = 1) | No changes in physical appearance (N = 3) | ||||
| No changes in odour (N = 3) | ||||||
| Ethanol | Aerosol penetration post sterilization exceeded 5% for particles >63 nm (N = 1)a | NIOSH standards maintained post sterilization (N = 1) | Relative bacterial survival rates of 68–89% depending on ethanol concentration (N = 1) | Fit factor >100 achieved for six replicate FFRs following one decontamination cycle, but not all six replicates achieved a fit factor >100 following two and three decontamination cycles (N = 1) | No changes in physical appearance (N =1) | Not assessed |
| Relative bacterial survival rates of 20–33% depending on ethanol concentration 24 h post sterilization (N = 1) | ||||||
| Viral levels below detectable assay limit (N = 1) | ||||||
| Isopropyl alcohol | Aerosol penetration exceeded 5% for particle penetration (N = 1) | Not assessed | Not assessed | Not assessed | Fading of ink strap (N = 1) | Not assessed |
| Aerosol penetration post sterilization exceeded 5% for particles >76 nm (N = 1)a | No changes in physical appearance (N = 1) | |||||
| EtO | No change in aerosol penetration post sterilization, aerosol penetration <5% maintained (N = 3) | No change in airflow resistance post sterilization, NIOSH standards maintained (N = 2) | No viable virus (N = 1) | Fit factor >100 achieved for four FFR models following one and three decontamination cycles (N = 1)b | No changes in physical appearance (N = 4) | Presence of ethylene glycol monoacetate on FFR straps, safety currently unclear (N = 1) |
| No changes in odour (N = 3) |
FFR, filtering facepiece respirator; H2O2, hydrogen peroxide; EtO, ethylene oxide.
N refers to number of studies.
a
Lin et al. used an challenge aerosol with a count median diameter of 101 ± 10 and a geometric size deviation of 2.01 ± 0.08, and evaluated penetration of particle sizes from 14.6 to 594 nm.
b
Based on normal breathing and deep breathing exercises only.