Diagnosing And Preventing Common Furnace Odors
Foul odors from the furnace can be alarming. Most furnace smells are harmless, although a few could signify trouble or even danger. This guide can help you identify the odor and its cause properly so you can take the correct steps to fix the situation.
A Dusty, Musty Smell
This odor is most common when the furnace is turned on for the first time for the season. It results from dust being burned off the burner, or from dust and mildew or mold spores from being heated inside the duct work. You can minimize it by changing the filters and vacuuming out the heat registers and exchanges before firing up the furnace in fall. If the odor persists for more than a day or two, you may need a professional duct cleaning.
These typically occur when you have an oil furnace with a clogged or old oil filter. Replacing the filter solves the problem. You can prevent it in the first place by having a full furnace inspection and tuneup annually. It also sometimes occurs when you turn on a brand new furnace, since parts may have been lightly oiled to protect them until installation. This odor should dissipate within a few hours.
You may sometimes get a smokey smell if your furnace vents through your chimney. This is usually caused by a blocked chimney. A chimney cleaning or a cleaning of the furnace vent through the chimney will remedy the problem. This can also occasionally happen in furnaces that have their own roof vent. For example, a bird may have built a nest in the top of the vent stack. Your heating services technician can clean out the vent and replace the cap, if necessary.
Plastic or Hot Metal Smells
These are indicative of overheating electrical wiring. Shut off the furnace and fan immediately. You will need to bring in a furnace technician to locate the source of the odor, since this is a major fire danger. Do not leave the house for a few hours after detecting this odor. You need to stay home and monitor the furnace to make sure a slow burning fire hasn't been sparked in the unit or in the walls.
Rotten Egg Odor
This odor is an emergency because it indicates a gas leak. Leave you home immediately – do not turn off the furnace, dial your phone, or turn off a light switch. These can all create a small spark, which can ignite the gas in the home and lead to an explosion. Go to a neighbor's home and call your local fire department or utilities emergency gas leak line.