由于说话产生的水滴沉降和蒸发而导致的病毒空气负荷
Viral air load due to sedimenting and evaporating droplets produced by speaking
摘要：
蒸发对液滴沉降时间的影响对于估计含病毒的空气飞沫的感染风险至关重要。对于100 nm < R < 60 μm范围内的液滴半径，蒸发可以用滞流近似描述，并且是扩散限制的。分析方程的液滴蒸发速率，随时间变化的液滴尺寸和沉降时间，包括蒸发冷却的显着效果。蒸发使大液滴沉淀的时间更长，从而显着增加了病毒的空气载量。根据最近对痰液中SARS-CoV-2浓度和说话时飞沫产生率的估计，一个感染者在不戴口罩的情况下不断说话，产生的总空气负荷超过10^4个病毒粒子。在一个中等大小的封闭房间里，这导致病毒吸入频率至少为每分钟2.5次。低相对湿度，如冬季在建筑物内和飞机上遇到的，会加速蒸发，从而使最初较大的水滴悬浮在空气中。
英文摘要：
The effect of evaporation on droplet sedimentation times is crucial for estimating the risk of infection from virus-containing airborne droplets. For droplet radii in the range 100 nm < R < 60 μm, evaporation can be described in the stagnant-flow approximation and is diffusion limited. Analytical equations are presented for the droplet evaporation rate, the time-dependent droplet size and the sedimentation time, including the significant effect of evaporation cooling. Evaporation makes the time for large droplets to sediment much longer and thus significantly increases the viral air load. Using recent estimates for SARS-CoV-2 concentrations in sputum and droplet production rates while speaking, a single infected person that constantly speaks without a mouth cover produces a total air load of more than 10^4 virions. In a mid-size closed room, this leads to a viral inhalation frequency of at least 2.5 per minute. Low relative humidity, as encountered inside buildings in winter and in airliners, speeds evaporation and thus keeps initially larger droplets suspended in air.
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