Why Your New Furnace Smells During First Few Runs

When you fire up your new furnace for the first time this heating season, do not be surprised if an unusual odour fills your home. That distinctive burning smell can be a normal part of your furnace’s break-in period in many cases, rather than a sign of malfunction, although you should still pay attention to how strong it is and how long it lasts.

New furnaces contain manufacturing residues that need to burn off during initial operation. These include protective oils, lubricants, adhesives, and coatings applied to components like the heat exchanger and blower motor during production. When your furnace reaches operating temperatures, these substances volatilize and create that characteristic chemical or burning plastic scent.

What to Expect During the Break-In Period

The smell typically appears strongest during your first few heating cycles, usually within the first day or two of operation. You’ll notice it most when your furnace runs for extended periods, which happens frequently during Ontario’s colder months when systems work harder to maintain comfortable indoor temperatures.

This break-in process often lasts for the first three to five heating cycles, although some homeowners report lingering odours for up to a week. The intensity should decrease with each use as residual materials fully burn away. Opening windows or running exhaust fans can help dissipate the smell more quickly, though this might seem counterproductive when you’re trying to heat your home.

The odour resembles burning metal, plastic, or paint as insulation materials and protective coatings cure under heat. While unpleasant, these smells are often related to small amounts of manufacturing oils and coatings burning off inside the furnace. If the odour is very strong, causes irritation, or does not fade after those first few runs, it is a good idea to have a qualified technician check the system.

When Normal Becomes Concerning

Not every furnace smell indicates normal operation. If odours persist beyond a week or intensify rather than fade, you may have installation issues or accumulated debris in your ductwork. Pay attention to the type of smell you’re experiencing.

Rotten egg odours can suggest a natural gas leak and require immediate attention: leave the home right away, avoid using electrical switches or open flames, and contact your gas utility’s emergency line or local emergency services from a safe location. Musty smells could indicate mould growth in your system or ducts. Sharp electrical burning scents might point to wiring problems, while metallic odours could mean mechanical friction or failing components.

If any smell accompanies symptoms like headaches, nausea, or dizziness, evacuate your home immediately and contact emergency services or your gas utility from outside the home. These symptoms could indicate carbon monoxide exposure, so do not re-enter until the home has been checked and you are told it is safe to go back inside. Make sure carbon monoxide (CO) alarms are installed and tested regularly in your home, and follow local code and manufacturer guidance on where to place them and when to replace them. Regular maintenance, including timely filter changes, helps prevent odour buildup from dust and debris throughout the heating season.

Expert Furnace Services in London, Ontario

If you’re experiencing odours from your new furnace, it’s essential to ensure everything is functioning correctly. At M&K Heating and Air Conditioning, we specialize in furnace installation in London and maintenance. Our experienced technicians help your system run safely and efficiently throughout the heating season.

Don’t let unpleasant smells disrupt your comfort. Trust our comprehensive services to keep your home warm and welcoming during the cold months in Ontario.