What Is Furnace Downdraft and How Do I Fix It?
BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning provides expert advice on this common question for homeowners in Greater Vancouver. If you need professional service, our licensed technicians are available across the region.
When to Call a Professional for Help
While understanding the answer to this question is helpful, some situations require professional expertise. If you are uncertain about any step, if the problem recurs, or if you notice any signs of gas odour, carbon monoxide, or electrical hazards, contact BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning immediately. Our licensed technicians across Greater Vancouver can provide expert diagnosis and repair. We recommend professional service for any issue that involves gas, electrical components, or safety-critical systems.
Related Services from BC Wide
BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning provides comprehensive furnace service across Greater Vancouver, including diagnostic inspections, emergency repairs, scheduled maintenance, and system replacement. Our Red Seal certified technicians service all major brands and carry OEM parts in their vehicles. For emergency service related to this question, call (604) 330-3953.
Answer: What Is Furnace Downdraft and How Do I Fix It?
Furnace downdraft occurs when combustion gases from the furnace — including carbon monoxide — are pulled back into the mechanical room instead of venting outside. This is most common with naturally drafted (atmospheric vent) furnaces where the flue relies on hot exhaust gases rising naturally up a chimney. Factors that cause downdraft include: a negative pressure in the home caused by kitchen or bathroom exhaust fans, dryers, or HRV systems that are depressurizing the mechanical room; a blocked or partially obstructed chimney; a chimney that is too short or terminates near a higher roofline that creates a pressure zone; or the house being tightly sealed (common in modern Vancouver homes) without adequate combustion air supply. A downdraft is a serious safety concern. Solutions include installing a power venter fan on the flue, adding combustion air from outside, or upgrading to a high-efficiency sealed-combustion furnace.
Safety Reminder
If you smell gas, suspect carbon monoxide or believe there is an immediate danger, leave the property and contact emergency services or the appropriate gas emergency authority. Do not remain inside — exit the building immediately and call for help from outside.