Air conditioning units that recirculate air in rooms and offices should be turned off or used only with open windows because of the risk of spreading coronavirus, experts advise.

They fear that any Covid-19 droplets in the air could be transmitted more easily to people in the room, even those who are socially distanced.

And they are advising office bosses to ventilate rooms with fresh air whenever possible.

The World Health Organisation (WHO) said this week that coronavirus can spread through tiny droplets floating in the air in enclosed spaces, after scientists highlighted the risk.
The UK Health and Safety Executive says the risk of air conditioning spreading coronavirus in the workplace is extremely low “as long as there is an adequate supply of fresh air and ventilation” but adds: “if you use a centralised ventilation system that removes and circulates air to different rooms, it is recommended that you turn off recirculation and use a fresh air supply”.

Some air conditioners take in air from outdoors and expel it again, while others, called split units, recirculate the same air.

Dr Shaun Fitzgerald, a fellow at the Royal Academy of Engineering, told the Telegraph: “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.”

This as a sizzling “heat dome” will be frying most of the continental United States for several weeks starting this weekend.

What this means is that over 80 percent of the U.S. population – encompassing 265 million people – can expect sweltering heat over the next week with highs exceeding 90. Another 45 million people will be facing highs in the triple digits.

Additionally, we can expect a full season of lethal heat ranging from 90°F to 121°F, not to mention extreme tropical storms, wildfires, and extreme weather related to La Niña conditions, reports the Independent.

On Friday, the National Weather Service issued excessive heat watch alerts for “dangerously hot conditions” and forecast that between Friday and Tuesday, over 75 record high temperatures would be reached or exceeded, with heat expected to increase in the following week.


On Saturday, temperature in Las Vegas reached a sweltering 112°F with the temperature expected to increase to 114°F on Sunday, while in Phoenix temperatures hit 115°F with Sunday expected to bring a withering 116°F before coasting at or above 110°F through the next week.

The new extremes sharply raise the danger of heat-related illness and death, further adding to the woes of hospitals struggling with surging COVID-19 infections in hard-hit regions and states like Arizona, California, Nevada and Texas.

“The heat wave will be very long-lived, lasting multiple weeks in some areas with only a few days of near-normal temperatures during that span,” Jeff Masters, Ph.D. and founder of the popular site Weather Underground, told CBS News.

 “This will increase the odds of heat illness and heat-related deaths.”

The news comes as many are already struggling to stay cool during the COVID-19 lockdown without air conditioning, or even the jobs and income to keep their AC units operational if they do have them.

Heat domes occur when the atmosphere keeps hot ocean air trapped as if it were under a lid or cap, with the end result being conditions of persistent high pressure and sustained heat for a prolonged period of time, sprawled over massive geographical regions.

To make matters worse, the larger the heat dome becomes, the hotter and more longer-lasting it will be.

According to a team of National Ocean Services researchers who set up the Modeling, Analysis Predictions and Projections program to figure out why heat domes occur, they found that the primary cause was strong changes in ocean temperatures from west to east in the tropical Pacific Ocean during the prior winter.

“This happens when strong, high-pressure atmospheric conditions combine with influences from La Niña, creating vast areas of sweltering heat that get trapped under the high-pressure ‘dome’,” the ocean service said.

Warnings of the brutal heat dome come one day after the NWS issued a La Niña watch Thursday predicting a 50 to 55 percent chance that the phenomenon would develop in the coming months, ensuring an intensification of the Atlantic hurricane season and a growing number of hurricanes and tropical storms.