Radon is caused by the decay of uranium in rocks and soil. It is present across Canada, seeps into homes from the ground and is known to cause cancer.
Knowing about the gas came too late for Al Huggett, a social worker in Prince George.
"We thought about getting testing, but we kept putting it off," he said. "It was not really high on our list of things to do."
Suddenly his wife, Sandra, became sick.
"Last year at about this time, she had a cough, pain in her chest," he said. "I took her to emergency. She had Stage 4 lung cancer."
The mother of two was a kindergarten teacher, avid about outdoor recreation and did not smoke.
"It was quite a shock," said Huggett.
Sandra Huggett died six months after being diagnosed, at the age of 54.
Doctors told her husband that radon was likely to blame.
"It is a leading cause of lung cancer in Canada," said Britt Swoveland, spokeswoman for the RadonAware program with the British Columbia Lung Association. "The No. 1 cause in non-smokers and never-smokers, the second leading cause behind tobacco."
The lung association has released to Prince George city council the results of tests done on 2,000 homes.
Thirty per cent tested higher than the national standard.
In the central part of the city — the V2M postal code — 56 per cent of homes tested higher than the national standard.
"It's naturally occurring, radioactive, tasteless, colourless, odourless," said Swoveland. "You just don't know it's in your house unless you test."
Tests cost $30 and dangerous homes can be fixed most of the time for less that $2,000. New building codes are being introduced that should prevent radon being a problem in new homes.
"There's tons of room for our society to do something about this issue," said Huggett. "It's not an expensive thing, but it would save thousands of lives."