Furnaces heat and distribute air through your home. Sometimes, problems can occur with a furnace that results in unpleasant or weird odors, either radiating from the furnace itself or blowing out of the ducts and vents. Here are four different furnace smells and what you might want to do about them!
Common Furnace Smells
This one is pretty straightforward: if you smell sulfur or rotten egg odor coming from your furnace or vents, you may have a natural gas issue. Whether the smell comes from your vents or from the furnace itself, shut the unit off immediately. Leave your home as quickly as you can, making sure to turn the gas off on the way out if possible. Then, call your gas company — they will be able to safely shut the gas off to your home so that a technician can diagnose the issue.
Natural gas leaks can result from a cracked or otherwise damaged heat exchanger or due to issues with the gas line itself. In either case, don’t try to diagnose the leak yourself. Instead, trained technicians have the equipment and knowledge to safely fix whatever’s wrong once the gas has been turned off.
Dusty Burning Smell
This is by far the most common of the furnace smells we encounter — for many people, this smell is an annual occurrence. During the summer months, furnaces typically sit unused. In many homes, particularly homes with pets and families, dust will begin to build up in the furnace. Once autumn rolls around and the furnace kicks in, all that dust gets burned away. Unless the furnace has been cleaned before getting turned on, you can expect to smell a funky, burnt dust smell for a few minutes the first time you run your unit.
There is little to no risk of fire or health concerns stemming from burnt dust. However, if the smell bothers you, you may want to book a furnace cleanup or tuning before turning your unit on for the first time. This ought to eliminate or minimize dust smells while also ensuring your furnace is operating safely and efficiently.
Moldy, Damp, or Funky Smell
While furnaces typically don’t have issues with moisture buildup, it’s not unheard of, particularly in high humidity areas. So if you smell a sour, earthy, or otherwise funky odor from your vents or furnace unit, you may have a moisture issue in your system.
Moisture is one of a few ingredients that contribute to mold and bacteria growth, the others being darkness, oxygen, and warmth. Unfortunately, your ventilation system has the last three items covered, so if moisture gets trapped in the system somehow, you can very quickly have a mold problem on your hands!
Before panicking, make sure that the source of the smell isn’t something more mundane. Are there any air intakes positioned near potentially smelly objects like garbage cans or compost bins? Is the scent localized to one room or area or present throughout the home? Once you’re reasonably confident that there aren’t any apparent sources for the odor, call a technician to inspect your vents and furnace. Fixing a mold problem involves removing the mold itself and diagnosing and fixing whatever moisture problem is present. If the source of excess moisture is a leaky pipe or damaged roof, the repair is simple enough. If the air in your home is too damp, a dehumidifier attachment will reduce moisture content in the air, preventing mold as well as improving your home comfort.
Another possible cause of funky, sour smells in your ventilation system is pest infestation. Rodents and other small pests can cause all sorts of damage to the ventilation system. Their urine and feces can collect in air ducts, spreading foul odors and potentially dangerous microbes through your home. Pests can die and decay inside ducts as well. An inspection will quickly identify any pest issue you may have.
Chemical/Burning Plastic Furnace Smells
If you smell a strange, acrid, burning plastic smell from your furnace, you may have an electrical issue: electrical components, particularly the blower fan, cycle on and off frequently. Over time, these components can wear out and become inefficient or perform poorly. As parts wear out, they can begin to generate more heat than usual. This can sometimes cause burning smells as the materials in the fan motor overheating.
Another possible cause of a burning plastic smell involves frayed or poorly connected wires in your furnace. Either of these issues can cause short fuses, damage other furnace components, or even cause electrical fires. If you smell burning plastic, turn your furnace off immediately and call a furnace repair technician!
Read more about common furnace problems, including unusual noises or how to choose a filter.