Department of Civil & Mechanical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
Department of Management Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
Int J Environ Res Public Health. 2023 Jan 29;20(3):2363. doi: 10.3390/ijerph20032363.
The importance of wearing a facemask during a pandemic has been widely discussed, and a number of studies have been undertaken to provide evidence of a reduced infectious virus dose because of wearing facemasks. Here, one aspect that has received little attention is the fraction of breathing flow that is not filtered because it passes as leak flow between the mask and face. Its reduction would be beneficial in reducing the dose response. The results of the present study include the filter material pressure loss parameters, pressure distributions under masks, and the fraction of breathing flow leaked versus steady breathing flow in the range of 5 to 30 L min, for two commonly used facemasks mounted on mannequins, in the usual 'casual' way and in a 'tight' way by means of three different fitters placed over the mask to improve the seals. For the 'casual' mount, leaks were high: 83% to 99% for both masks at both exhalation and inhalation flows. For the 'tight' mount with different fitters, the masks showed different lower levels in the range of 18 to 66% of leakage, which, for exhalation, were nearly independent of flow rate, while for inhalation, were decreasing with increasing rates of respiration flows, probably because suction improved the sealing. In practice, masks are worn in a 'casual' mount, which would imply that nearly all contagious viruses found in aerosols small enough to follow air streams would be exhaled to and inhaled from the ambient air.
在大流行期间佩戴口罩的重要性已被广泛讨论，并且已经进行了许多研究，以提供因佩戴口罩而减少感染病毒剂量的证据。在这里，一个关注较少的方面是由于口罩和面部之间的泄漏而未经过滤的呼吸气流的比例。减少这种比例将有助于降低剂量反应。本研究的结果包括过滤材料压力损失参数、口罩下的压力分布以及在 5 至 30 L/min 的范围内，两种常用口罩在通常的“随意”方式和通过放置在口罩上的三个不同的贴合器以“紧密”方式安装在人体模型上时，泄漏呼吸流与稳定呼吸流的比例。对于“随意”安装，泄漏很高：两种口罩在呼气和吸气时的泄漏率均为 83%至 99%。对于使用不同贴合器的“紧密”安装，口罩的泄漏率在 18%至 66%的范围内显示出不同的较低水平，对于呼气，几乎与流速无关，而对于吸气，随着呼吸流速的增加而降低，这可能是因为吸力改善了密封。在实践中，口罩以“随意”方式佩戴，这意味着气溶胶中足够小以跟随气流的几乎所有传染性病毒都会被呼出并从环境空气中吸入。
