Relative Humidity 40% – 60%

In environments with lower than 40% Relative  Humidity (RH), droplets from a cough or a sneeze  lose their moisture quickly. This results in droplets  becoming ‘dry aerosols’ and capable of staying in  the air for longer periods. Viral particles remain  infectious much longer below 40% and above  80%. 

Virus particles are most inactive at 50% humidity,  and retain their infectiousness the further from  that median value, plateauing at 20% and 80%,  respectively2. Staying within 40% to 60% relative  humidity is ideal from a comfort perspective but  50% is the most ideal in terms of fast virus  inactivation.

Keeping the humidity at the ideal range not only  helps you stay comfortable but also keeps you  healthy. Low humidity (less than 30%) may  promote dry nasal passage which makes people  more susceptible to cold viruses while high  humidity (more than 70%) may promote mold  growth which can be harmful to people with  weakened immune systems.