What Causes a Burning Smell When I Turn on My Heater

Winter is upon us and if you have not yet, you will soon be turning on your heater. Smelling something burning in your house is never a good thing to smell. If you have noticed a burning smell from your ducts or other parts of your HVAC system, you may have an issue. So, what does it mean if your furnace and heating make your house smell like something bad is happening? What should you do about it, and why is it happening?


How Does Central Heating Work?

Central heating systems can work in the same general way as central cooling systems by moving air around to change the temperature in your home. Instead of moving hot air out, central heating systems move hot air in to get your home to your desired temperature. But, keep in mind; this is not always the case. Depending on which central heating system you own, your HVAC device might actually be producing its own heat.


The Two Basic Types of Heat Systems

Basically, there are two kinds of heating systems, forced air and radiant.

  • Forced Air Systems

These systems use a blower or fan to pull air into the system where it is heated and circulated throughout the home. They can be noisy with metallic squeaks from loose connections and require routine air filter changes to keep them running well. But because they heat the air, they tend to warm up homes quickly. A forced air system is composed of air return ductwork, a blower, a heating or cooling unit with heat exchangers housed inside the air handler cabinet, a plenum where the air exits the air handler, and supply ductwork. The supply ductwork carries the air to all the rooms of the home while the return ductwork carries all the air from the rooms back to the blower and air handler.

  • Radiant Systems

These systems rely on the use of heat to move air through convection. Basically, heated air rises and is replaced by cooler air, which is heated and rises and so on. Because these systems work passively, they tend to heat rooms slowly. Plus, they do not filter dust or allergens from the air, and in some cases, are not as energy efficient. However, most are inexpensive to buy, install, and maintain.


What Causes the Burning Smell?

During the summer months, especially in Southern California, most people do not use their heating system. When the system is not in use, dust and other debris will settle in and on the equipment. If you have pets, some of the dander can get circulated and settled in the system when you run your air conditioner. Even if you keep your home immaculate, dust and debris will build up. When you turn on your furnace for the first time, the layer of dust and debris will burn up and cause your heater to smell like burning dust. You should just smell this for the first time when you start your heater and should disappear within one hour.

If this smell lasts longer or persists beyond an hour, you will need to check other elements in the HVAC system. If left unchecked, the smell could indicate that there is something wrong with one of two things: not enough airflow through filters due for any number of reasons. The simple solution is to change the filter.

The other reason may be an issue with the motor. A quick inspection of the motor should tell you if additional issues require a technician to check.


Not So Normal Odors

While that initial dusty/burnt smell is fairly common, there are some not-so-normal odors you should be aware of as well:

  • Electrical, Metallic or Plastic Burning Smell

Electrical burning smells are very distinct, and every homeowner can identify the smell. If you smell the burning electric smell when you engage your furnace, turn the unit off immediately and call Aire-Tech for service. You should never risk using the furnace if it is emitting an electric smell.

Electrical smells are also very similar to heated mechanical smells. Follow your nose to locate the source. If it is coming from your furnace, it could be an overheated motor, worn bearing or a wiring issue. If it is coming from a specific register/vent, it could be a plastic toy or other foreign object in the duct.

  • Musty/Moldy/Locker Room Smell

If you smell a musty odor, your air filter could be overly dirty, or you may even have a little mold or bacterial buildup in your HVAC system. Check and replace the filter if needed. Another source could be organic growth on the cooling (evaporator) coil or in your ductwork. Both of those will require professional cleaning by an HVAC contractor or duct cleaning specialist.

  • Rotten Eggs/Sulfur

Any time you smell rotten eggs or sulfur when gas appliances are in the home, it is time to leave the premises and call the gas company – immediately. Gas leaks are dangerous and should always be handled by trained professionals. Many furnaces are now electric units, so people do not have to worry about gas leaks anymore. However, for those who are still using a gas furnace, this smell indicates a potential for fire or explosion. Discontinue use immediately and call for service.

  • Chemicals

If there is a chemical odor that smells like formaldehyde, your furnace most likely has a cracked heat exchanger. A cracked heat exchanger is extremely dangerous for two reasons. First, it can fill your home with carbon monoxide. Second, it can cause a fire in your home. At Aire-Tech, we take cracked heat exchangers very seriously. If one of our technicians finds a cracked heat exchanger out in the field, he is required to shut down the system immediately until a field supervisor can confirm the cracked heat exchanger. Please do not hesitate to call if you discover this issue.

  • Dirty Socks

The smell of dirty socks is never pleasant. It is especially unpleasant when it is circulated throughout your home. What is the culprit? When your furnace coils cycle between heating up and cooling down, it creates condensation that allows bacteria to grow. Bacteria build up in your system over time and cause the smell. An annual maintenance completed by trained technician should take care of this problem. During an annual maintenance, your furnace coils are cleaned. It is also important to keep up on changing your furnace filter regularly.

  • Burning Smell That Lasts More Than One Day

If the burning smell you encountered on the first day you turned on your furnace continued, you might need to check the air filter in the system. It may be clogged with dust that is continuing to burn off when you use the system. This can be eliminated quickly by changing the filter.

If it is not the filter and you still smell the burning smell, it is time to call Aire-Tech for service. Your system may need a deep cleaning on the interior that we can provide, or it may require a more serious repair.


Can I Avoid the Burning Smell?

While you cannot avoid every burning smell every time, there are ways that you can reduce it. The best way to ensure that the burning smell is minimalized is to have yearly furnace maintenance performed on your system. This will include things like cleaning the system’s interior, which will help to minimize dust and other debris.

You should also set a regular schedule to change out your furnace filter. This will help to ensure that dust particles are captured and do not recirculate. If you have a dirty filter, this will cause dust to sit around, causing an increased burning smell. Furnace filters should be changed at least every three months. If you have a less-than-high-quality filter, you will want to change it monthly. A good idea is to get a washable filter for your furnace that can be washed frequently to ensure adequate airflow. In addition to preventing dust buildup in your unit, a good clean air filter will help to protect the components in your furnace.


Getting Rid of a Burning Smell from Your Furnace

As the homeowner, you can change the filter to help with dusty smells. For most anything else, you should call a heating technician to be safe. Here are the steps to follow:

  • Turn Off the Furnace

Avoid the temptation to keep the heater unit running while you search for the source. Be safe, turn off the furnace, and then visually inspect for the cause or call a professional.

  • Look for Active Fire or Smoke

Rule out an active emergency and call 9-1-1 if you do find anything dangerous!

  • Inspect for Burn Damage

After the furnace has been off for a while (so you do not risk touching hot parts), inspect the equipment and any nearby objects for signs of burning or melting to give you an idea of the location and extent of the damage.

  • Clean the Air Filter and Equipment

Some furnaces are difficult to clean without professional equipment, but you may be able to dust and wipe down some dusty parts.

  • Call a Heating Repair Service

If your issue is not just a dusty air filter, that burning smell is telling you that your furnace has a problem. Call a pro if anything seems less than ideal, or if the smell comes back.


Give Us a Call

One of your worst fears has to replace the heater or air conditioner in your home. But with due diligence, you can prevent a premature replacement and the associated costs.

If your system needs repair or inspection, call Aire-Tech on 951-926-1002. You can also visit our Contact page and complete the contact form.