Measurement results at room temperature 20ºC: Relationship between humidity and aerosol lifetime
・Aerosolization of pure water to an average particle diameter of 5 μm
・Experiment conducted with a flow velocity of 0.5 m/s and a pipe length of 1 m
・Measurement by particle counter P8-506
・Sampling at 0.2, 0.7, 1.2, and 2.2 elapsed seconds
・Additionally assumed that the residence time in the measuring instrument is 200 ms
・At 20% humidity, most particles evaporate within 1 second
・Most of the particles evaporate within 2.4 seconds at 40% humidity or less
・When the humidity is above 60%, there is almost no decrease with evaporation
・After evaporation, only the impurity cores in the aerosol are expected to be floated
Measurement results at room temperature 20ºC: Relationship between humidity and particle diameter change
・Aerosolization of pure water to an average particle diameter of 5 μm
・Experiment conducted with a flow velocity of 0.5 m/s and a pipe length of 1 m
・Measurement by particle counter P8-506
・Sampling at 0.2, 0.7, 1.2, and 2.2 elapsed seconds
・Additionally assumed that the residence time in the measuring instrument is 200 ms
・Particles with a smaller diameter have a longer residual time with humidity
・As the particle diameter increases, the number of observations itself decreases in a low-humidity environment
=> The time required to halve the size of particles with a diameter of 5 μm to 2.5 μm is less than 0.4 seconds
On the other hand, the particle size distribution was largest at 2.5 μm at most of the measurement points, and there was no noticeable trend of the distribution shifting toward a smaller diameter
Diffusion of COVID-19
・When the humidity drops below 50%, the particle diameter rapidly decreases from the moment it leaves the mouth, making it easier to diffuse.
・A droplet of 5.0 to 2.5 μm loses its water content in 0.4 seconds.
・Infectivity is maintained even at low humidity.
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・Heating by air conditioning causes a sudden drop in humidity, so it is important to control humidity when air conditioning is used.
・It is important to maintain a humidity level of 50%.
・Masks are also important because it can easily protect diffused droplets with Virus.
・For areas where ventilation is limited, air purifiers are needed.
Conclusion
・Heating by air conditioning causes a sudden drop in humidity, so it is important to control humidity when air conditioning is used.
・It is important to maintain a humidity level of 50%.
・Masks are also important because it can easily be diffused.
・For areas where ventilation is limited, air purifiers are needed
