How will actual wearing time influence the protective effect of surgical masks?

The protection effects of wearing masks against viruses and bacteria have been verified many times over previous pandemics and infectious diseases. However, the supply of the surgical masks can barely meet the surging demand at the early stage (first 12 months) of the outbreak of a pandemic. Thus, it is essential to use surgical masks wisely in such urgent times. In this work, we selected two types of surgical masks and systematically explored how actual wearing time influences the protective performances of the masks. Each type of surgical masks was worn for 4, 10, 24, 32 and 48 h, respectively, and the results show that with the increase of actual wearing time, both particulate filtration efficiency (PFE) and bacterial filtration efficiency (BFE) of the masks decline. After wearing for 32 h, the PFEs of both types of masks were still far above the corresponding standard (≥30%, according to YY0469-2011). After wearing for 10 h, the BFEs of both masks were over 95% (which is regarded as the safe value), whereas after 24 and 32 h of wearing, the BFE of one type of mask decreased obviously to 91.6% and 80.0%, respectively. Based on these results, it is rational to conclude that the wearing time of surgical masks should be no more than 10 h.