Air conditioning units that recirculate the same air in a room should be switched off or only used with open windows, experts have urged, amid mounting concern around the role of airborne transmission to spread Covid-19.
Experts told the Telegraph that air conditioning units that only used recirculated air could exacerbate the spread of virus particles if someone was infected with Covid-19.
Dr Shaun Fitzgerald, a fellow at the Royal Academy of Engineering, said there were two types of air conditioning units – ones that take air in from outside and expel it out again, or those that recirculate the same air.
This second type, known as a “split” unit, draws air in, passes it over cooling coils and sends it back into the room.
Guidance from the Chartered Institution of Building Service Engineers, which Dr Fitzgerald helped draw up, warns that split air conditioning units that do not have a “dedicated source of outside air supply into a room… could be responsible for recirculating and spreading airborne viral particles into the path of socially distanced users”.
Dr Fitzgerald said that it may go against conventional wisdom and be more expensive, but opening a window while operating the unit was the best way to mitigate risk.
“The recommended strategy now, if you have one of these split units, is to throw the window open and sacrifice your desire for a cold or cooler environment. If there is a modicum of wind it will move the air around. If you can’t open a window turn the unit off.”