Why does my smoke alarm go off when furnace starts?

Usually it's dust burning off the heat exchanger after months of inactivity. This typically clears within 5-15 minutes of operation. However, persistent smoke or burning smells could indicate overheating, dirty filters, or serious issues requiring immediate attention.

When should I call emergency HVAC service?

Call emergency service immediately if you see visible smoke from the furnace, carbon monoxide detector activates, persistent burning smell continues, burner flames are yellow/orange instead of blue, or anything makes you uncomfortable. Better safe than sorry with furnace safety.

Can a cracked heat exchanger cause smoke?

Yes. A cracked heat exchanger is dangerous and produces smoke, persistent burning smells, yellow burner flames, and can trigger CO detectors. This requires immediate professional repair or replacement as it poses serious health and safety risks.

Is it normal for furnace to smell when first turned on?

Yes, a brief dusty or burning smell during first use each season is normal as accumulated dust burns off. The smell should dissipate within 15 minutes. If it persists, worsens, or you see smoke, turn off your furnace and call for service.

Why does my smoke alarm go off when furnace starts?

Usually it's dust burning off the heat exchanger after months of inactivity. This typically clears within 5-15 minutes of operation. However, persistent smoke or burning smells could indicate overheating, dirty filters, or serious issues requiring immediate attention.

When should I call emergency HVAC service?

Call emergency service immediately if you see visible smoke from the furnace, carbon monoxide detector activates, persistent burning smell continues, burner flames are yellow/orange instead of blue, or anything makes you uncomfortable. Better safe than sorry with furnace safety.

Can a cracked heat exchanger cause smoke?

Yes. A cracked heat exchanger is dangerous and produces smoke, persistent burning smells, yellow burner flames, and can trigger CO detectors. This requires immediate professional repair or replacement as it poses serious health and safety risks.

Is it normal for furnace to smell when first turned on?

Yes, a brief dusty or burning smell during first use each season is normal as accumulated dust burns off. The smell should dissipate within 15 minutes. If it persists, worsens, or you see smoke, turn off your furnace and call for service.

When Your Furnace Kicks On and the Smoke Alarm Starts Screaming

When your furnace fires up and the smoke alarm suddenly screams, it's terrifying. Is your house on fire? Is your furnace dangerous?

What's Probably Happening

Harmless: Dust Burning Off

The most common cause is dust settling on the heat exchanger during the off-season. When your furnace starts for the first time after months of not running, that dust burns off.

This is usually harmless but annoying. The smell typically goes away after 5–15 minutes of operation.

Concerning: Overheating

If your furnace is overheating:

Dirty filter: Restricts airflow, causing heat to build up
Ductwork issues: Blocked ducts cause pressure problems
Motor problems: A failing blower motor creates excessive heat

Serious: Cracked Heat Exchanger

A cracked heat exchanger is a safety hazard. Signs include:

Consistent burning smell (not just on startup)
Smoke visible at the furnace
Yellow or flickering burner flames (should be blue)
Carbon monoxide detector activation

When to Call for Service

Call EMERGENCY if:

Visible smoke from the furnace
Carbon monoxide detector going off
Strong persistent burning smell
Yellow or orange burner flames
Anything that makes you uncomfortable

Call for regular service if:

Dust smell persists throughout the cycle
New burning smell that wasn't there before
Frequent cycling on and off

Contact Galaxy Heating & Air Conditioning for any furnace concerns – better safe than sorry!

When Your Furnace Kicks On and the Smoke Alarm Starts Screaming

When Your Furnace Kicks On and the Smoke Alarm Starts Screaming

What's Probably Happening

Harmless: Dust Burning Off

Concerning: Overheating

Serious: Cracked Heat Exchanger

When to Call for Service

About the Author

Galaxy Heating & Air Conditioning

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