With the advent of longer, cooler nights, families are firing up their furnaces and putting logs in the fire.
While most people protect themselves from fire by installing smoke detectors, few Canadians prepare for the dangers of carbon monoxide poisoning - often called the silent killer.
This toxic gas is produced from incomplete combustion due to insufficient oxygen. Difficult to detect because it's colourless, odourless and tasteless, it's the most common cause of fatal poisoning.
Recent building-code changes require new homes to include carbon-monoxide detectors. But a report by the Canadian Association of Fire Chiefs indicates 60 per cent of homes don't have one.
"It is highly recommended that people install a carbon monoxide detector on every level," said Ken Gill, fire-prevention officer with the Oak Bay Fire Department.
"Carbon monoxide is called the silent killer because it is a neutral-weighted gas that mixes freely with air. You can't smell it or see it. Firefighters treat a call to a carbon monoxide alarm very seriously. We would respond to a carbon monoxide call with appropriate breathing apparatus."
Initial symptoms of mild poisoning include light-headedness, headaches and malaise. Because the symptoms are similar to effects of the flu, most people ignore initial warning signs.
Exposure to concentrations of 100 parts per million or greater is dangerous and can lead to death. But low, long-term exposure is equally hazardous, Gill said. Exposure to low levels of carbon monoxide over time can lead to depression, confusion and memory loss - even heart damage.
The main culprits are faulty forced-air furnaces that burn home-heating fuel, such as oil or natural gas. Dangerous concentrations can also form if a chimney from a wood-burning stove is blocked.
Gill said the fire chiefs' report indicates 44 per cent of homeowners don't have their furnaces checked annually.
Carbon-monoxide detectors are easy to purchase from any hardware store, and can be plugged into an ordinary wall power outlet. The detectors should be placed in or near bedrooms, with at least one on each level of a house, including the basement.
They should not be placed near cooking appliances or in very humid areas such as bathrooms. Most detectors are set to warn occupants at the lowest level of what is considered dangerous.
Prices range from $23 for a portable, battery-operated unit to $60 for a talking smoke/carbon monoxide 120V direct-wire unit with battery back-up.
When it comes to fire, smoke detectors remain the first line of defence in the home. The technology hasn't changed much over the years, but detectors can now be wirelessly connected, so when one alarm sounds, all the alarms in the house sound.
Another version comes with a remote control to silence an alarm without having to climb a ladder.
A crowded and competitive market means basic smoke detectors can sometimes be purchased for as little as $7.50. The low price means homeowners have no excuse for not having several detectors. The Association of Fire Chiefs recommends that people replace their units every 10 years. Newer units come with an expiry date, but older units don't.
"If in doubt about their age, I would recommend people replace them," Gill said.
Older detectors are prone to be overly sensitive because of dust build-up, so it's a good idea to vacuum them occasionally with the cover on. Firefighters' greatest fear is that people will disable a smoke detector after a number of annoying false alarms.
While regular battery replacement is recommended - one way to remember is to change it every time there is a time change - some new smoke detectors now come with a lithium battery that will last 10 years.
Those unsure about how many and where to put their smoke detectors should call their municipal fire departments, Gill said.
"We are always happy to conduct a home visit to help assess a homeowner's fire-safety needs."
