Five Sherbrooke residents were ordered from their homes after high levels of carbon monoxide were detected on Tuesday evening. But the deadly gas did not come from their buildings — it came from nearby construction on their street.
One person was briefly hospitalized after showing some symptoms of poisoning. Residents of two of the three affected homes have since been allowed to return, but one woman is still out of her house as a precautionary measure.
The incident happened after construction crews dynamited part of Albert-Skinner Street, where the city is carrying out the work to modernize the sewer system and is changing some aging pipes.
Stéphane Simoneau, Sherbrooke's fire chief, said carbon monoxide is created when dynamite is combusted.
"The blast creates pressure in the ground that pushes the gases to move up toward the house pipes, the sanitary and drainage pipes," he said. "Sometimes, like yesterday, we have an accumulation that manages to sneak into residences."
Simoneau said it's not an uncommon phenomenon.
Just last week, five other homes in Sherbrooke were evacuated for the same reason and another three households were evacuated in mid-August.
Provincial norm in place
While there's not much that can stop carbon monoxide from leaking when blasting is going on, Simoneau said Sherbrooke has contingency measures to ensure the safety of its residents if it does happen.
For example, the city forces any contractor doing blasting work to install carbon monoxide detectors within 100 metres of the site.
This measure is actually a norm stipulated by Quebec's agency for standardization and certification, the Bureau de normalisation du Québec (BNQ).
"Contractors are fully responsible for damages caused by their activities and that of their employees," the norm reads. "As a contractor, you are responsible for ensuring the implementation of measures to prevent carbon monoxide poisoning during excavation work done through blasting."
Simoneau said Sherbooke also helps residents relocate if they're forced out of their homes as a result of high gas levels.
He said the fact that the city was able to get the five residents out quickly and unharmed on Tuesday proves the measures in place work — and are important.