I just read a an article on the Australian ABC News site encouraging people to decrease their heating bills in winter here in Australia by sealing up air leaks from ventilation ducts, holes from appliances and sealing fireplaces when not in use.
Many years ago I left a radon monitor run over a weekend in my office in Darwin. At that time I was the Senior Health Physicists in the Department of Mines and Energy with a remit to oversee the radiation in the Uranium Mines in the Northern Territory, so I had access to thousands of radon level measurements in the open cut uranium mines done around the clock.
What was interesting was the radon levels in my office went up over the weekend when the airconditioning was turned off. Radon is a radioactive gas like helium and is produced from the decay of radium 226 in hard rocks like the aggregate used in concrete and sometimes as an an impurity in gymsum used in pasterboard.
What I found was the peak levels in my office were higher than the average levels in a uranium mine. It was not that the levels in the uranium mine were high – they were remarkably low, but the levels in the office were easily measurable.
In California, the prevalence of basements in houses meant the trace amounts of radium in some soils could produce undesirable levels of radon in the houses and a Radon Certificate was required when selling the house. Some water supplies in Australia have elevated levels of radon and place like laundries can experience elevated radon levels. A bit like gas being related if you shake a carbonated drink. Some Australian caves also have high radon levels.
Sealing a house can make the number of air changes an hour drop from around 3 to a much lower figure and allow radon levels to build up, particularly if the house has a cellar or if the building materials contain things like granite.
The upshot is that making a house more energy efficient for people working at home during the COVID-19 pandemic can create a hidden danger. The risk is small but quantifiable.
ARPANSA, the nuclear regulatory authority in Australia offers detailed advice on radon: https://www.arpansa.gov.au/understanding-radiation/radiation-sources/more-radiation-sources/radon
There would also be an increased danger oof release of combustion
