Updated October 2, 2026.

To prepare your furnace before winter in Durham Region, check the filter and thermostat, keep airflow paths clear, test your carbon monoxide alarms, and arrange a professional inspection before you depend on the heat every day. Homeowner checks are useful, but they do not replace servicing of a gas furnace.

Your pre-winter furnace checklist

• Check the filter. Turn the system off before accessing it. Follow your furnace and filter manufacturer’s instructions for the correct size, installation direction and replacement schedule. Wash a filter only if its instructions identify it as reusable.
• Check the thermostat. Select heating mode and a temperature above the current indoor temperature. Confirm that the furnace responds. Note any error message or unexpected cycling for your service appointment.
• Keep airflow clear. Move furniture away from supply registers and return grilles. Keep storage away from the furnace and its service access.
• Check outdoor vents. Keep intake and exhaust openings clear of leaves, snow and debris. Do not dismantle venting or attempt to repair it yourself.
• Test carbon monoxide alarms. Follow the alarm manufacturer’s testing instructions and check its expiry date. A working furnace is not a substitute for a working alarm.

Carrier’s furnace maintenance guidance separates routine homeowner care from an annual professional tune-up. Enbridge Gas’s Ontario safety checklist also recommends a yearly furnace inspection before heating season.

Leave the heat exchanger and gas components to a professional

Do not brush or vacuum the heat exchanger, adjust gas valves, clean burners, or bypass a safety switch as a homeowner task. A qualified technician should inspect the combustion system, heat exchanger, venting and electrical components using the appropriate procedures and instruments. See our furnace maintenance guide or request a service appointment for this work.

What to do if something is wrong

If the furnace does not heat, makes an unusual noise or repeatedly stops, record what you notice and arrange furnace repair. Do not repeatedly reset a furnace that is shutting down on a fault.

If you smell natural gas, leave the area immediately. From a safe location, call Enbridge Gas at 1-866-763-5427 or 911. Do not try to diagnose the appliance. If a carbon monoxide alarm sounds, leave the building and call 911 from a safe location, as explained in Enbridge Gas’s carbon monoxide safety guidance.

Prepare for your service appointment

Have the furnace model, any error code and your last service date available. Tell the technician whether the problem affects the whole home or particular rooms. Ask what the inspection includes and request approval of any repair quote before additional work begins.

For homeowners in Whitby and the surrounding Durham Region, contact Aire One East Heating and Cooling at 905-576-7600 to discuss a pre-winter service appointment.