According to an advisory of government ,
the temperature of air-conditioners should be set in between 24 and 30 degree celsius and relative humidity of between 40 and 70 per cent this summer. This comes after The Central Public Works Department (CPWD) issued the advisory to its officials in an office memorandum to address the concerns associated with the spread of the covid-19 via ACs and ventilation systems.
According to the Indian Society of Heating Refrigerating and and Air Conditioner Engineers (ISHRAE) , the best way to minimise the risk of virus spread is by ventilation of indoor environments with outdoor air.
In humid climate, the temperature should be set closer to 24 degrees for de humidification, while closer to 30 degrees in dry climates and use of fans to promote sir movement.
A study was done in China, in which it was found that the transmission was lower in 100 cities with high temperature and high humidity.
It also quotes a study that shows the SARS-CoV-2 can live for 14 days on a surface at 4 degrees Celsius, one day at 37 degrees Celsius and will die in 30 minutes at 56 degrees Celsius.
According to it humidity can affect the infectivity by the ease with which infection takes place, through respiration.
In an environment with low humidity, the foreign particles can invade the body with more ease. Thus, relative humidity of at least 40 per cent is considered the threshold.
“When we breathe dry air the mucous membrane in the lungs become dry. The fluid over lining the cells becomes more viscous, and the little hairs called cilia, which protect our lungs from deep settling of viable and non-viable particles, cannot work and particles settle more deeply in the lungs,” it states. “If we consider oxygen and CO2 transport and the blood, it is only one cell membrane that separates the airspace from the blood. So, if something goes from our lungs into the blood, we get infected.”