After exposure to air, KN95 masks can be reused for a limited number of times as long as they are not used during aerosol generation and are not contaminated with patient body fluids, but at the same time increase the risk of surface contamination by pathogens. Currently, OSHA does not have any standards for disinfecting KN95 masks, but NIOSH notes that mask manufacturers may give recommendations for maximum reuse, but in the absence of these recommendations, the recommended maximum number of reuses per mask is limited to five to ensure safety. CDC recommends no reuse in general situations, but in emergency situations, such as when masks are scarce, they can be cleaned and reused . People have been trying to explore the cleaning of masks, but there are also concerns that this may reduce the filtering performance of masks or deform masks . Researchers at Duke University have published a way to clean KN95 masks without damaging them by using vaporized hydrogen peroxide, allowing for a limited number of reuses . The U.S. National Institutes of Health has found three methods of disinfection that allow KN95 masks to be reused a limited number of times: hydrogen peroxide, dry heat at 70 degrees Celsius, and ultraviolet treatment. However, if the KN95 mask is disinfected with alcohol, the charge in the mask will be removed, making the mask unable to absorb particles, so it cannot be disinfected with alcohol. Steam disinfection and boiling water treatment above boiling water, little charge loss, acceptable.