3 Furnace Odors Every Homeowner Should Know

Technician servicing the gas boiler for hot water and heatingYour heating system is supposed to make your home more comfortable, but foul odors emanating from your ducts may do just the opposite. Odors can be harmless, but they often indicate an issue with your furnace. In some cases, the issue may even be dangerous. Learn to recognize the possible odors so you can be prepared with the right course of action if a foul smell ever comes from your furnace.

1. Rotten Eggs

The most alarming odor you can smell from a furnace is that of rotten eggs or sulfur.

Possible Cause

The cause is likely a gas leak of some kind, typically natural gas. Natural gas is odorless in nature, but sulfur is added to natural gas intended for home use as a safety measure. Propane has a similar odor added for the same reason. If your furnace runs off of natural gas or propane, then the smell of rotten eggs is a major safety concern.

What to Do

Do not stay in the home if you suspect a gas leak. Open a door or window and shut off the gas supply to the home, if it is safe to do so. Do not turn on a light switch or appliance or even operate your phone inside the house. Even a small electrical surge can ignite the gas in the air. Evacuate your home and call the 911 or the gas utility emergency line.

Once the gas is properly shut off by the utility, your furnace company can repair the leak in the appliance.

2. Burning Odor

There are two common types of burning odors from a furnace — the metallic-like smell of burnt metal or the odor of burning oil.

Possible Cause

A metallic odor likely emanates from an electrical short, whereas the smell of burning oil is most likely from within the combustion system. Both can pose a major problem. If the burning smell is more reminiscent of singed hair or has musty overtones, it’s likely the result of dust on the furnace burner and it is of little concern.

What to Do

Although both types of odors are a concern and the cause can pose a risk, you probably aren’t in any immediate danger. If you suspect an electrical short, turn off the furnace and do not operate it again until you can have it inspected and repaired. Continuing to use a furnace that is shorting can lead to a fire.

If you suspect that the oil used to fuel the furnace is the origin of the odor, there may be several causes. In some cases, the smell is the harmless burnoff of some spilled oil from your last fill. In other cases, odors may indicate a leak in the fuel tank, a problem with the valve regulating oil delivery, or a crack in the burner. Repair is necessary before you can use the furnace again.

3. Dirty Socks

The smell of dirty socks is a common enough problem in HVAC systems that it has been dubbed “dirty sock syndrome.”

Possible Cause

Dirty sock odors develop when bacteria grows on moist surfaces, so it is more common in the AC system rather than the furnace. Occasionally, though, condensation can build up in the ducts leading from the furnace from the temperature fluctuations between cold and warm.

Bacteria can grow on the dust and moisture in the ducts, which results in the spread of the dirty sock odor when the hot air blows it from the duct system and into your home.

What to Do

Although not dangerous, the odor is unpleasant. Special coatings can be applied to the coils if the odor is found to be emanating from inside your HVAC system.

If the odor is coming from your duct system, then you may need to schedule a full duct cleaning in order to fully eliminate the foul smell.

Contact us to schedule a furnace tune-up and maintenance visit today.

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Steele Brothers Heating Inc