NEW DELHI: Amid common concerns associated with air-conditioning, ventilation and the spread of coronavirus , a think tank has recommended that the air-conditioner temperature should be ideally set between 24 and 30 degree and humidity should be maintained between 40% and 70%.The central public works department (CPWD), which is responsible for maintaining all central government offices and official accommodations, has shared the advisory with all its field officers for guidance and use.The guidelines have been prepared by Indian Society of Heating Refrigerating and Air Conditioner Engineers (ISHRAE).Referring to several studies, the guidelines suggest that survival of virus decreases progressively at moderate temperatures of 20.5 to 24 degree centigrade and further decreases at more than 30 degree centigrade temperature.It says to limit the risk of Covid-19 infection by air, it’s better to ventilate indoor environments with outdoor air as much as possible. “Mechanical ventilation systems and air conditioning systems, which provide ventilation, can perform this function more effectively than simply opening the windows , because they improve the quality of the outdoor air with filtration,” the guidelines mention.The guidelines recommend that rooms should be kept well ventilated when the AC is not running. They say that the desert coolers which are also called evaporative coolers must draw air from outside to ensure good ventilation. In the case of fans, these should be operated with windows kept partly open.For industrial units, it has recommended maximum ventilation with outdoor air.