Why Is There A Burning Smell When I Turn On The Heat

When winter approaches and the temperatures start dropping, you’ll likely fire up your heating system for the first time in many months. While the feeling of warm air is enjoyable, it’s sometimes accompanied by a burning smell in your house that can be strange or unpleasant. This doesn’t necessarily mean you need to call the fire department, but you shouldn’t ignore the smell, either. Some odors are normal, and others are signs of potential danger.

Keep reading to learn about the various smells that can occur, what they mean and whether they require any action.

Is It Normal for Your Heater to Smell Like It’s Burning?

Should the heater smell like it’s burning? The answer to this question is sometimes yes and sometimes no. For instance, if you turn on your heater for the first time of the season and smell burning dust, this is completely normal. It just means there’s dust in your heating unit, which is harmless and should burn off quickly. If you smell an electrical burning smell, on the other hand, this is not normal at all. It could be a sign of a serious electrical issue that could lead to a fire.

Heating units can also emit a variety of other smells, each of which we’ll cover in the following section.

Why Does It Smell When I Turn on the Heat?

Smells from your heater can come from a variety of sources, including dust or mold within your system, a blocked exhaust vent or an electrical malfunction. Here are some common causes of a burning smell when you turn on the heat and what you should do in each situation.

1. Burning Dust Smell

The burning smell coming from your heater most often occurs when the heating is turned on for the first time in the winter season. If many months have passed since its last use, dust and other types of debris may collect on the burners, heat exchangers, air ducts and other components of the heating unit. When you turn the furnace on, this dust and debris burn off, releasing a smoky odor.

If you smell burning dust, don’t worry. Once the dust and debris have burned off, the odor should go away. However, if this odor lingers around or becomes stronger, try changing out the air filter. If the smell persists after the air filter has been switched, turn your unit off and contact an HVAC expert to perform emergency maintenance.

2. Musty Smell

If you turn your furnace on for the first time of the season, it may smell musty, which indicates mold or mildew. It could be either in the heating unit itself or in the ductwork. It could also be trapped on the furnace filter or humidifier pad, if your unit has one.

Sometimes, the mold and mildew is attached to the debris that will burn off eventually. However, if this odor doesn’t go away, the first thing you should do is clean or replace your air filters. If the filters are brand new or cleaning them doesn’t remove the smell, contact an HVAC expert to perform a professional cleaning and inspection of your system.

To avoid this musty smell in the future, make sure to inspect the filter regularly and replace or clean it whenever necessary. Either dispose of the humidifier pad or if its washable, create a solution that’s equal parts water and vinegar. Stick the filter in the solution and clean it gently.

3. Electrical Burning Smell

If there is an electrical burning odor coming from your heater, this could be harmless or something very serious.

In some cases, this smell can come from a foreign object in the ductwork of your HVAC system, which will begin to smell as it heats up. Take out your registers and inspect them visually to clean or remove objects that don’t belong.

In other cases, an electrical burning smell could indicate a serious electrical issue. If you’ve ever been outside during a thunderstorm, you’ve probably smelled ozone, which is somewhat similar to chlorine. Your heater may produce a similar smell if it overheats.

As your heater gets older, a worn bearing might make the blower motor bind or seize up. It may then draw extra electricity to help it push through the resistance, and that additional voltage could lead to an excessive buildup of heat.

This heat can be enough to melt the insulation on the wires, and soon your heating unit could produce sparks and electrical shorts that emit the odor. If not dealt with, these melting wires could produce enough heat to be dangerous.

If you smell an electrical burning odor and it is not the result of something stuck in the ductwork, immediately turn your unit off and contact an experienced technician.

4. Rotten Eggs Smell

If you have a gas – or propane furnace that’s giving off a sulfur or rotten eggs smell, this is a probably sign of a natural gas leak. You should leave the premises immediately and call your gas company. Do not try to pinpoint the leak yourself, and do not return to the house until you’ve been told it’s safe to do so. Gas leaks can be extremely dangerous and should always be left to the professionals.

Natural gas is extremely flammable, and its combustibility is why it makes such a great fuel source for appliances in your house. Unfortunately, this gas can also be dangerous if inhaled, causing nausea, dizziness, irregular breathing and fatigue.

Natural gas doesn’t have an odor of its own, which is why gas companies add the pungent chemical mercaptan for safety. This chemical is sulfur-based and gives off the distinct odor of rotten eggs, letting you know that natural gas is nearby.

5. Pet Odors

Sometimes turning on your furnace will produce the odor of pet hair or waste. If you smell this whenever you turn on your furnace, take a look at the ventilation registers on the floor level. There’s a good chance that there’s a mess by this vent, and cleaning it up should solve the issue.

6. Sewage Stench

If you get a whiff of sewage coming out of the vents, there might be a broken wastewater line or open sewer line not far from the heating system. Quickly inspect the external vents, which should help determine the source of the odor. You might need to contact a plumber to fix the problem.

7. Smell of Chemicals

If you smell chemicals after turning on your furnace, this is definitely something you shouldn’t ignore. If the odor has a distinct chemical smell similar to formaldehyde, chances are that your furnace’s heat exchanger is broken. The heat exchanger functions by cycling heat from the combustion chamber into the plenum, and if this part is broken, the risk of fire increases dramatically. Carbon monoxide fumes may also be released, which have no odor or color.

If you smell chemicals, turn the furnace off immediately, open some windows and contact your HVAC professional right away. Follow these steps to stay safe from Carbon Monoxide.

8. Smoke Smell

If you smell smoke coming from your furnace, immediately turn it off and open some windows. This smell may occur if the furnace chimney, also known as an “exhaust vent” or “flue pipe,” is blocked. The combustion exhaust from the furnace has to go somewhere, and if it can’t escape through the flue pipe, it is forced to go elsewhere.

In such a situation, it is critical to assess your safety. For instance, if the odor is faint, just open some windows for ventilation and contact a professional. However, if the smell comes suddenly or is strong, it would be safer to leave your home temporarily until a technician arrives and determines the source of the smoke.

9. Oil

If you smell oil after turning on your heater, this likely means the filter on the furnace is clogged. If you change out the filter, the smell should go away. However, if the new filter doesn’t do the job, speak with an HVAC professional.

When to Call an Expert

Some smells go away fast or just require a quick fix, but others mean you should call a professional – often immediately. Here is a closer look at which smells require a professional and which ones likely don’t:

• Burning dust: In most cases, you do not need to call an expert. This smell is usually the result of accumulated dust on burners, air ducts or other furnace parts, and it should burn off quickly. If the odor lingers, switch the air filter. If the smell still doesn’t go away, contact an HVAC professional to inspect your unit.
• Mold or mildew: In most cases, there is no need to contact an expert. If you smell mold or mildew after turning on your heater, treat it like burning dust — first, wait for it to burn off on its own. If it doesn’t burn off, then try changing out your air filters. If the musty smell is still around, call a local professional.
• Electrical burning: Whether you call a professional depends on the situation. If you notice a foreign object in the ductwork, such as a toy or spill, and removing it causes the smell to go away, then no further action is required. However, if you cannot find any objects in your ductwork — or removing the object does not make the smell go away — this could indicate a serious electrical issue. You should turn off your unit and contact an HVAC expert immediately. An electrical issue can cause the blower motor to bind or seize up, which forces the unit to draw extra electricity. This can cause the unit to overheat and melt the insulation on the wires, leading to the production of electrical shorts and sparks. That is likely the source of the odor, and it will need professional attention.
• Rotten eggs: If you smell rotten eggs, evacuate your home and call your gas company immediately. There is most likely a leak in a natural gas line. While you may be tempted to go shut off your natural gas line, its combustibility poses too great a risk to your safety. You should go outside and remain there until you the gas company says it’s safe to go back in.
• Pets: If you smell pet odors when you turn on your heater, there is no need to call an expert. Instead, go examine your heater’s ventilator registers on the floor level. Chances are this pet smell is coming from a mess located next to or near the vent. Clean it up, and the smell should go away.
• Sewage: If you smell sewage when turning on your heater, you may need to call an expert plumber, as this stench may indicate a open sewer or broken wastewater line. If you look around the heater’s external vents, you may be able to pinpoint the source of the smell.
• Chemicals: If you smell chemicals, particularly one similar to formaldehyde, you should definitely call an HVAC technician right away. But first, don’t forget to turn the heater off and open up some windows. The smell of a formaldehyde-like chemical probably indicates a failure of your heat exchanger, which dramatically increases the risk of a fire. This could also be accompanied by carbon monoxide fumes, a notoriously lethal gas.
• Smoke: If you smell smoke, call an expert. However, before you call, it’s important to ensure your safety, which will depend on the intensity of the smoke. If the odor isn’t too strong, just open up a few windows for ventilation before calling. If the smell is strong and appears suddenly, however, then we recommend that you leave your home immediately and stay there until the technician arrives and fixes the issue. Smoke coming from a heater is usually caused by a blockage in the flue pipe, which forces the smoke to escape out through the ductwork.
• Oil: If you smell oil, check your filter before you call an HVAC professional. Often a clogged filter can cause the smell. If you just change out this filter, then the odor should disappear. However, if the smell persists, call an HVAC technician, as it may be a sign of an oil leak.

How Zimmerman Can Help

The smells coming from heating units can indicate a lot of different types of problems — some of which need the professionals at Zimmerman Plumbing and HVAC. If you’re a homeowner living in and around Harrisburg, PA, you can trust our reliable HVAC repair and maintenance services and plumbing solutions.

We also strive to provide you with the best customer service possible by providing free estimates, emergency after-hour services and planned maintenance agreements. To get in touch with us, feel free to fill out our form or, if it’s a more urgent matter, call us at (717) 696-0101. We look forward to assisting you with your HVAC and plumbing needs!