Common Furnace Smells: What They Mean and What to Do

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As with most appliances, furnaces can emit a number of different odors. These smells can indicate various issues that might be affecting your heating system. Some of these problems are simple fixes, but others are serious and potentially life-threatening.

Knowing how to identify a problem based on the smell your furnace is giving off will not only save money, it might also save your life.

Low Priority Smells

Low to High Priority Chart
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Often, smells are a result of poor maintenance routines and easily fixed. It is easy to forget about the furnace when summer is here and neglect filter changes and other maintenance tasks. The following smells are most often caused by simple oversights.

Dusty Smells

Dust has a habit of accumulating over time, and your furnace is no exception. Running it for the first time in the winter season can result in the layer of dust and dirt to be burned off. This is quite normal and usually dissipates within a few hours.

Changing your filter will usually solve the problem if it doesn’t go away on its own. In the rare instance the dusty smell remains even after changing filters, you should call a service technician to do a deep cleaning and make sure there are no other problems.

Musty Smells

This is another common odor caused by long periods of inactivity. The usual culprit is a dirty filter, which should be replaced to prevent mold spores from polluting the rest of the house.

In some cases, the mold or mildew is somewhere in the vents, which will be more apparent if you can only smell it in certain rooms. This matter is a little more serious, and you should have your vents and ductwork cleaned to avoid mold-related illnesses.

Oily Smell

This is a common odor associated with clogged filters in oil furnaces. While oil furnaces are not as popular as they once were, they may still be found in older homes and more remote areas.

This smell generally isn’t a sign of danger, but if it persists after changing your filter, call a technician to ensure there are no leaks or other issues.

Smoky Smell

This is an uncommon odor found mostly in homes which still have functional fireplaces or an oil furnace. A blockage in the chimney can cause smoke to back up into your HVAC system. Having the chimney cleaned should solve this problem under most circumstances.

If this is a recurring problem, you may wish to have the chimney capped to help prevent debris or pests from getting in.

High Priority Smells

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Some odors are a clear indication that something has gone very wrong with your furnace. These smells are quite distinct and are a warning to shut your furnace down immediately and call in a professional.

Electrical or Metallic Smells

On some occasions, your furnace may overheat or begin to break down from age. This leads to two distinct warning smells that are similar to burning wires.

In the case of an electrical smell, some of the components in your furnace are overheating. Many furnaces have a built-in shut-off to prevent permanent damage to these components. You will want to call a technician to examine your furnace for the cause of overheating and replace any damaged parts.

Likewise, metallic smells are caused by rubber or metal components that have begun to break down due to age. What makes this issue serious is that the smell indicates these parts are actually burning as opposed to simply overheating. Although this is a high priority issue, the damaged parts are usually easy and cheap to replace.

Rotten Eggs

Even in the best of times, the smell of rotten eggs indicates a gas issue. This holds equally true of bodily, sewage, and mechanical sources. Gas companies add sulfur dioxide to their otherwise odorless natural gas to alert homeowners of any problems.

When your furnace kicks on, and you get that unmistakable stench, it is a clear indicator of a leak. Shut off your furnace immediately and avoid creating sparks or open flames until the leak is repaired. You will also wish to ventilate your home and call both a service technician and your gas company.

In many cases, the gas company will shut off your gas supply until the repairs are made, as working with gas leaks can be extremely dangerous. This can be frustrating in extremely cold weather, so you may wish to stay with friends or at a motel if the technician cannot affect repairs for a few days.

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