Heat sterilization dramatically reduces filter efficiency of the majority of FFP2 and KN95 respirators

BACKGROUND: Shortages in personal protective equipment, especially respiratory protective devices (respirators), occurred during the initial phase of the coronavirus disease 2019 pandemic. Sterilization of used respirators can reduce these shortages. In this study, respirator testing was carried out after a single cycle of sterilization. AIM: To determine if steam sterilization and re-use can be applied safely for used respirators. METHODS: An aqueous solution of NaCl (0.02% w/v) was nebulized and passed through a sample of respirator material in a cabinet. Passing particle concentrations were measured directly from the cabinet and via the filter material of the respirator for particles ≥0.3 μm, ≥0.5 μm and ≥1.0 μm in diameter. FINDINGS: Only three of 10 steam sterilized respirators met the requirement of 94% filtration efficiency. CONCLUSION: Heat sterilization cannot be applied generically for safe re-use of respirators.