Recharging N95 masks using a van de Graaff generator for safe recycling

N95 respirators, used in the current COVID-19 pandemic, filter virus-containing aerosols using the static electricity of melt-blown polypropylene sheets. Their shortage at hospitals demands their recycling, but the standard sterilization methods, including alcohol spraying, washing, autoclaving, and heating in hot water, cannot be easily implemented because they compromise the electrostatic charges and thus their filtering effect. We report that a van de Graaff generator, commonly used for the demonstration of static electricity, can be used as a safe, cheap and quick method to recover the polypropylene electric charges that are lost during sterilization processes. We will show that this recharge also restores the masks' filtering function.