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Ventilation, humidity key in AC rooms: Govt guidelines
The guidelines are part of recommendations by the Indian Society of Heating, Refrigerating and Air Conditioning Engineers (ISHRAE), which said that people at home can maintain humidity levels by keeping a flat pan filled with water out in the room.
Rooms and offices with air conditioning must be well-ventilated and humidified, according to government’s guidelines to public sector offices after a report by a group of experts outlined precautionary measures that need to be taken to curtail the possible spread of Covid-19 in such environments.
The recommendations come after scientists in China’s Guangzhou found that 9 of 90 people having lunch at a restaurant on a particular day contracted the coronavirus disease from an infected person because they were sitting in the same air current, a finding that has prompted worry over closed spaces such as offices, hospitals and even homes.
According to the guidelines issued to the central public works department, the Union government asked air-conditioning units to be set at 24°C and 30°C and relative humidity to be maintained between 40-70% in all government buildings. The guidelines added that some windows should be open or exhaust units activated to ensure fresh air circulation.
The guidelines are part of recommendations by the Indian Society of Heating, Refrigerating and Air Conditioning Engineers (ISHRAE), which said that people at home can maintain humidity levels by keeping a flat pan filled with water out in the room.
While using an air conditioner unit at home is safe, central air conditioning in large offices, malls, and hospitals can raise the risk of an infection, especially if the air blows over groups of large people or if there is little fresh air.
Many hospitals have shut centralised air conditioners to ensure there is no circulation of the virus between Covid-19 and non-Covid-19 areas. “We have stopped the central air conditioning in the suspected Covid-19 ward and the screening area. Window air conditioners have been installed here. As for the trauma centre, it is a Covid-19 hospital, so the central air conditioning is running,” said Dr DK Sharma, medical superintendent, All India Institute of Medical Sciences (AIIMS).
At Lok Nayak and Rajiv Gandhi super-specialty hospitals, all central air conditioning have been switched off.
“There is a problem when it comes to centralized air conditioning in hospitals because most do not have proper filters. So, window AC can be used in Covid-19 wards, to at least separate them from the rest of the areas. In fact, in Covid-19 wards – pumps and filters should technically be used to create negative pressure just like in bio-safety laboratories,” said Dr Shobha Broor, former head of department of microbiology at AIIMS.
The ISHRAE guidelines suggest maintaining positive pressure in non-Covid-19 areas and negative pressure in areas with Covid patients, so that infected air from the room does not leak out and infect others.
The study in Guangzhou found that while the air conditioning air flow played a part in the spread of the infections, the AC ducts itself had no traces of the virus. The concern, according to the researchers, appeared to be of virus droplets spreading through wind in enclosed places.
