Why Does the Furnace Set off the Smoke Detector?

This needs to be separated into three different categories to understand why the furnace sets off the smoke detector, how to prevent it from happening and whether or not it is dangerous. If you have a combination smoke and carbon monoxide detector go to the CO2 page here.

Floor Furnace

If your floor furnace sets off the smoke detector, don’t panic, it is probably just some debris stuck down in it that is smoldering a little bit. Grab a flashlight and look through the floor grilles and examine what is lurking in the heat exchanger area. You should easily be able to see the problem. Before addressing and cleaning up the debris remember to turn off the floor heater and let it cool down.

Once the heater is cool feel free to remove the floor grill and vacuum clean the inside of the furnace. If the item is melted on (most likely this is caused by a small plastic toy) you will have to scrape it off. Do not use flammable cleaners. The floor furnace has a pilot light and there is a possibility that you could cause an explosion. Put the furnace back together again and turn it up. If the problem is gone you have fixed it.

If the floor heater continues to set off the smoke detector give us a call and let us check it out. You may be having a vent issue and the interiors of your wall where the vent goes up could be starting to burn. We have uncovered many floor furnaces over the years that were burnt without anyone knowing it. If you haven’t had your furnace checked out this year you should give us a call. It is very important to have a full safety check up on your floor furnace each year.

Wall Furnace

It is not unusual for a wall furnace at the beginning of the season to set the smoke detector off. This is usually just a matter of dirt buildup during the summer time burning off with just enough smoldering action to set off the detector. Open your home up and keep the furnace burning for a 30 minutes watching it carefully. This should not be a problem for you. If it happens a second time, give us a call as you are having an issue that needs to be addressed. Most of these problems that reoccur are from improper venting and improper venting from a wall furnace means filling the home with carbon monoxide. Have your wall furnace checked out every year and make sure that you have the required carbon monoxide detector installed in your home.

Forced Air Furnace

Call us. You have an issue. The only time that a forced air furnace should ever set off a smoke detector is when it is first installed. Occasionally the metal of the heat exchanger had alight coating of oil on it from the manufacturing process. If this is heavier than normal it can create enough smoke to set off the alarm. If your forced air furnace is setting off the smoke detector make sure to unplug it. When a forced air furnace sets off a smoke detector it is typically suffering from an electrical short circuit and the wires, transformer or controls are burning. It may still run, for now, but letting it go means letting your furnace continually damage itself. The sooner the problem is discovered and repaired the cheaper and more successful the repair will be.

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Burning smells are not the same as setting off the smoke detector. This dirty coil left a very bad smell in the home when the heater was running, but it still would not set off the smoke detector. This blocked so much airflow that some of the control on the furnace started to melt because of the elevated temperatures. HVAC maintenance every year is critical.

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