4 Strange Smells You Might Notice When Turning on Your Heat — And What They Mean
When the cold Ontario winter arrives, turning on your heating system is essential for keeping your home warm and comfortable. But if you’ve noticed an unusual smell when the furnace kicks on for the first time, you’re not alone. Many homeowners experience odd odours at the start of the heating season — some of which are completely normal, while others can signal a potentially serious issue.
Here’s what those strange smells might mean and when you should call a professional.
1. Dusty or Burning Smell — Usually Normal
A mild dusty or burning smell is the most common scent homeowners notice when they first turn on their heat, and it’s usually harmless. After months of inactivity, dust and debris settle on the furnace’s heat exchanger, burners, or other internal components. When the system starts running, those particles burn off and create a temporary odour.
This smell should disappear after a few hours or within a day or two. If it lingers longer than 48 hours or becomes stronger, it could indicate an underlying problem like dirty burners or overheating components — and it’s worth scheduling a professional inspection.
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2. Musty or Mildew Smell — Possible Mold or Bacteria
A musty, damp, or “dirty socks” smell typically points to microbial growth inside your HVAC system. This often happens when moisture builds up in your ductwork, air handler, or heat pump coils, providing the perfect environment for mould and bacteria.
If the smell doesn’t go away after a few hours of operation, start by replacing your air filter. Persistent odours may require a professional cleaning and duct inspection to prevent allergens from circulating through your home and to restore indoor air quality.
3. Rotten Egg Smell — Gas Leak Emergency
A sulphur or rotten egg smell is one of the most serious warning signs and should never be ignored. This smell often indicates a natural gas leak, which is highly dangerous and can lead to fire, explosion, or carbon monoxide poisoning.
If you notice this odour:
Turn off your furnace immediately.
Do not use any electrical switches or open flames.
Evacuate the home and call your gas company or emergency services.
Contact a licensed HVAC technician once it’s safe to return.
Even a small gas leak is a serious hazard — don’t take chances.
4. Electrical Burning Smell — Sign of a Serious Problem
A burning plastic or electrical smell often means there’s an electrical issue inside your heating system. This could be due to frayed wiring, a failing blower motor, or overheating electrical components — all of which can cause fires if left unchecked.
If you smell burning plastic, turn the system off immediately and contact an HVAC professional. Continuing to run the furnace could result in permanent damage or significant safety risks.
Final Thoughts: When in Doubt, Call a Professional
Not every smell means there’s an emergency, but it’s always better to be cautious. While dusty odours are normal early in the season, musty, sulphuric, or electrical smells should always be taken seriously. The safest approach is to have your heating system inspected before winter begins to catch issues early and ensure everything is running efficiently and safely.
At Climate Works Heating, Cooling & Plumbing, we offer comprehensive furnace inspections, cleaning, and maintenance services across Ontario. Whether it’s your first time turning on the heat or you’re responding to a strange odour, our certified technicians will diagnose the problem and keep your home warm — and safe — all winter long.
Frequently Asked Questions (FAQ)
Is it normal for my furnace to smell when I first turn it on?
How can I prevent weird furnace smells in the first place?
What should I do if I smell gas?
Can a musty smell affect my health?
Should I turn my system off if I smell burning plastic?
Need Help Keeping Your Home Warm This Winter?
Staying comfortable in an Ontario winter doesn’t have to mean sky-high energy bills. At Climate Works Heating, Cooling & Plumbing, we’ve helped thousands of families across Ottawa and the GTA keep their homes warm and efficient all season long.
From furnace tune-ups to heat pump installations, our team of experts is here to help. Call us today or schedule a service visit to make sure your home is ready for the cold.
Contact Us
Ottawa (Headquarters)2639 Pollock Rd.
Richmond, ON, K0A 2Z0
info@climateworks.ca | 613-838-9989
Toronto & GTA
1883 Mattawa Ave.
Mississauga, ON, L4X 1K8
gtaestimating@climateworks.ca | 437-317-0699
