The London Fire Department says recent plunging temperatures have sent carbon monoxide (CO) calls soaring.

Officials have reportedly responded to over two dozen calls in the past week related to CO, and say in many cases it has been found in the homes.

A number of causes have been identified, including:

  • broken or malfunctioning heaters
  • vents blocked by snow and ice
  • people warming up vehicles inside a garage or near a basement window

Fortunately, none of the cases involved toxic levels, and the fire department is crediting CO alarms with preventing harm.

"Never take chances when it comes to the threat of carbon monoxide," Rick Jefferson, London Fire's public information coordinator, said in a statement. "If your alarm is sounding, immediately get everyone out to fresh air and call 911. Leave windows and doors sealed so that, if there is carbon  monoxide present, firefighters should be able to detect and trace it to the source."

Fire officials are reminding residents that as of Oct. 2014, CO detectors became mandatory in most homes.

CO alarms are  required outside of any sleeping area in any residence with a fuel burning appliance like a natural gas furnace or hot water heater, gas or wood fireplace, or with an attached garage.

In multi-family buildings with fuel burning appliances, alarms must be installed in service rooms and near sleeping areas in units adjacent to them.