Disinfection and reuse of filtering half masks

Respiratory protection devices, such as filtering half masks, are used in the health care system to protect the user from infectious agents. The masks must obtain adequate sealing on the face and consist of a well-functioning filter material to work optimally. They are composed of several layers of mainly polypropylene, and the filter properties are based on a combination of mechanical and electrostatic properties.

Filtering half masks are normally not approved for reuse, but in a pandemic situation where supplies could be insufficient, disinfection and reuse may be necessary. National and international communities have proposed and discussed several technologies and procedures in connection with previous pandemic situations, and recently with the ongoing spread of the SARS-Cov-2 virus. Norwegian Defence Research Establishment (FFI) have reviewed the research on disinfection and reuse of filtering half masks to assess which techniques that should be further investigated and possibly implemented in Norway.

A suitable disinfection method must not destroy the respiratory filtering properties or adversely affect the facepiece fit. The method cannot cause contact hazards or evaporation of chemicals to be safe for the person to use the respirator. At the same time, the disinfection method must effectively inactivate both SARS-Cov-2 and other infectious agents.

A number of methods for disinfecting filtered half masks have been tested and described in the literature. The methods show very different effects on the masks. The disinfection methods with negative effects on the masks cause the filter properties to deteriorate or disappear almost completely, the masks remain contaminated with chemicals that are harmful to the health or the masks change shape in such a way that it is not possible to achieve good fit.

Based on available literature and research, FFI consider that the disinfection methods that have little or no effect on the mask's physical properties after disinfection are ultraviolet radiation (UVC / UVGI), hydrogen peroxide vapour (HPV), moist heat (60-70 °C), and dry heat (<80 °C). Methods that may have adverse effects on the masks, or have other significant drawbacks, are disinfection with ethylene oxide and liquid hydrogen peroxide. Disinfection with alcohol, soap and water, hypochlorite solution and autoclaving have strong negative effects on the masks.

It is important to be aware that the filtering half mask response to the different disinfection methods will not necessarily be the same for different mask types. Since they do not contain exactly the same materials, it can affect how each product responds. It will therefore be important to test, validate and document how disinfection methods affect each product.