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About Me : At present, it's believed that both N95 mask and medical surgical mask can effectively protect the user from the new coronavirus if using them correctly. Structurally, the filter layer of those masks (N95 and medical surgical mask) is formed of non-woven fiber material, which may make tiny particles adhere to its fiber. Breathing air isn't obstructed and may easily undergo the filter material. The mechanism of filtration is especially inertial collision, diffusion and electrostatic adsorption. The premise of using the mask again after disinfection is that the sterilized mask can neither affect the free circulation of air nor destroy the filtering mechanism of the mask. So, what quite disinfection can meet these two points?
To find out the influence on the filtration mechanism of masks (N95 mask and medical surgical mask), five disinfection methods were compared: 1) oven dry heat disinfection, 2) alcohol spraying disinfection, 3) steamer wet heat disinfection, 4) heat and high-pressure disinfection and 5) ultraviolet disinfection.
1. it had been found that dry heat disinfection (heating at 70 ℃ for 30 minutes) had the smallest amount effect on damaging the filtering mechanism, and therefore the filtering effect might be maintained above 95%.
2. The disinfection method of spraying alcohol on the mask will destroy the electrostatic absorption of the mask, causing filtering efficiency of the mask lowering below 95%.
3. Other methods like steamer damp heat method and high-pressure heat sterilization methods also made the filtering efficiency of the mask less than 95%.In addition, heat and high-pressure method makes the mask seriously deformed.
4. The new coronavirus is sensitive to ultraviolet rays, and ultraviolet disinfection doesn't affect the filtration efficiency of respirators. However, the inactivation effect of viruses in mask fibers, which can't be directly observed, is unknown. Therefore, it's not recommended.
The new coronavirus is sensitive to heat. It can effectively inactivate the new coronavirus by heating for half-hour at 56 degrees Celsius. Therefore, the only dry heat sterilization (70 degrees Celsius heating for 30 minutes) can effectively inactivate the virus without affecting the protective function of the mask. However, it's uncertain whether several times of disinfection affects the protective effect of the mask.
On February 9th 2020, Fudan University Shanghai Medical College, Ministry of Education / Medical Molecular Virology Laboratory of Health Committee and faculty of Public Health together published a research project paper "Experimental research on safe and rapid regeneration of disposable medical masks". it had been published within the Journal of Microbiology and Infection online version. The research paper confirmed that disposable medical masks might be disinfected by using following method: After using the mask, it are often wrapped with household fresh-keeping bags and treated with household electric hand blower for half-hour . then it are often used again. This method doesn’t affect masks original filter retention effect, and therefore the contaminated viruses are inactivated!