For most processes in electronics manufacturing, a relative humidity of 50 - 60% is ideal (Fig. 1). Air that is too dry leads to electrostatic charges, machine stoppages, increased dust attraction and health hazards. Additionally, air that is too dry makes it easier for viruses to spread. Viral respiratory infections are almost exclusively transmitted from person to person indoors. The most common route of infection is airborne transmission at close range via droplets and at long range via aerosols. Depending on the size of the particles, this is referred to as droplet or aerosol transmission. Due to their small size, aerosols are particularly light. Virus-laden aerosols can spread in the air over a considerable period of time in large rooms. Relevant for the spreading are the air movements and the air humidity, which have a direct influence on the range, floating ability and infectivity of the aerosols.
"A minimum air humidity of 40 - 60 %is an important component of quality assurance and additionally protects employees from respiratory infections."
The lowest transmission risk exists at this minimum air humidity. This is also the range in which the human immune defense is most effective due to the self-cleaning of the mucous membranes. Aerosols essentially consist of water, salts and proteins. At a relative humidity of < 40%, aerosols lose their water content and dry out. Dry aerosols are formed, which are smaller and lighter and can fly longer through the room. Air currents and movements of room occupants also cause dry aerosols to be more quickly re-suspended from surfaces and further dispersed.
If the topic of "air humidity" has not yet had the importance it deserves in electronics manufacturing, it is gaining in significance as a result of the current pandemic.
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16 April 2021