Filtering facepiece respirators decontamination using a low-temperature-steam-2% formaldehyde sterilisation process during a pandemic: a safe alternative for reuse.

BACKGROUND: the COVID-19 pandemic has caused problems with respirator supplies. Reuse may minimise the impact of the shortage but requires the availability of an efficient and safe decontamination method. AIM: our objective is to determine whether the low-temperature-steam-2%-formaldehyde (LTSF) sterilisation process is effective, preserves the properties of filtering facepiece (FFP) respirators and allows safe reuse. METHODS: 14 unused FFP2, FFP3 and N95 respirator models were subjected to two decontamination cycles. After the second cycle, each model was visually inspected and accumulated residual formaldehyde levels were analysed according to the EN 14180. After one and two cycles, Fit factor (FF) was tested on all models and penetration tests with sodium chloride (NaCl) aerosols were additionally performed on five models. FINDINGS: decontamination physically altered three of the 14 models. All the residual formaldehyde values were below the permissible threshold. Irregular FF decreases and increases were observed after each cycle. In the sodium chloride (NaCl) aerosol penetration test, three devices obtained equivalent or superior results to those of the FFP classification with which they were marketed, both at the baseline level and after one and two decontamination cycles. Two other devices reduced their filtering capacity. CONCLUSION: One and two sterilisation cycles using LTSF do not alter the structure of most (11/14) respirators tested and did not degrade the fit or filtration capacity of any of the analysed respirators. The residual formaldehyde levels comply with the EN 14180 standard. This reprocessing method could be used in times of shortage of personal protective equipment.