Gas furnaces produce an open flame, high temperatures and sometimes furnace odor. It may be a harmless consequence of simple maintenance issues or it may be an ominous sign of danger. For example, a cracked heat exchanger is hazardous because, in addition to leaking odors, it may allow deadly carbon monoxide gas to permeate your home. The heat exchanger may emit the smell of burning metal or gas combustion. Since carbon monoxide is odorless, however, the most dangerous consequence is that it may emit no smell whatsoever, while still exposing your family to dangerous CO gas. Treat any and all furnace smells with respect and call your HVAC contractor when you notice them. Here are some other common causes of furnace odor:

• At seasonal startup, dust accumulation in the combustion chamber and return ducts is commonly burned off in the first hours of operation. The smell is best described as a dry, dusty odor and usually dissipates quickly. Changing the filter before starting up after a long idle season may help prevent the occurrence. If the odor persists, shut down the furnace and call your HVAC contractor.
• If the dry, dusty burning odor continues, the burner in the furnace may be drawing in a continuous supply of dust from dirty return ducts. Before investing in duct cleaning, however, an inspection by an HVAC professional should always be conducted to visually verify the presence of excessive dust accumulation.
• Overheating resulting from too many closed supply registers can also produce a burning smell as hot air builds up, overheating ducts and other components. The rule of thumb is that no more than 20 percent of the supply registers in a home should be closed at once.
• A binding furnace blower motor may overheat and disperse odors that smell like an electrical fire throughout the system ducts. Blowers should be lubricated once a year, a standard item on an annual furnace maintenance procedure.

Smoky Mountain Heating & Air services the interior comfort and indoor air quality needs of Asheville homeowners. Contact us for more information about avoiding the potential hazardous consequences of gas furnace odor.

Our goal is to help educate our customers in Asheville, North Carolina and surrounding areas about energy and home comfort issues (specific to HVAC systems).

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