Facebook tracking pixel
(707) 539-4533 |  Sonoma Napa and Marin Counties

updated February 2023

What to Do if My Furnace Smells Like Burning in Santa Rosa?

This might sound like kind of an odd question since oil and natural gas furnaces do use combustion to generate heat for your home. However, these furnaces are designed to burn cleanly and without any odors that could bother the homeowner. That means that, if you’re smelling a burning odor coming from your furnace, something is probably going wrong. A modern furnace, no matter what fuel source it uses, should never create a strong burning smell while it’s running. If you do detect that smell, you should immediately turn the furnace off and get in touch with your HVAC repair company right away.


Luckily, Santa Rosa doesn’t get too cold during the winter, so you should be fine going without a furnace for a few days until a technician can take a look at it. However, even if it does get extra chilly, you need to make sure you keep it off until it’s been checked out. There are a few different root causes for a burning smell inside the furnace, and several of them can be pretty severe fire hazards. Faulty heating equipment accounts for close to 15% of all house fires in the US, and you could end up losing your home, belongings, or even your life if you allow the furnace to keep running.


Here’s a little information on what can cause that burning smell and how you can deal with it once it starts:

Why Does My Furnace Smell Like Burning?

Most furnaces generate heat by burning fuel, usually natural gas but sometimes heating oil or even old-fashioned wood pellets. These days, manufacturers take great care to make sure that the combustion reactions are completely isolated inside a special chamber of the furnace so no fire escapes. Even pilot lights have become a thing of the past, replaced by electric igniters that only spark when they really need to. That means that, if you’re smelling something burning in the furnace, something has either gotten into the combustion chamber or the heat from the fire has been allowed to escape the chamber or the heat exchanger. Either way, the problem will have to be addressed one way or another. Here’s a quick rundown of a few different causes for a burning smell in your furnace:



This is the most benign cause of a burning smell and the only one that doesn’t require immediate support from an HVAC technician. In relatively mild climates like the Santa Rosa area, most homeowners spend a good section of the year with their furnaces switched off. Depending on how well you handle the cold, you might switch your furnace off around March and not turn it back on again until October or even November. This is actually a good thing in most ways since it allows you to save some money on your monthly power bills and reduces the wear and tear on the internal workings of your furnace. However, that long break between March and November allows plenty of dust to build up inside the furnace itself, including important parts like the igniter, heat exchanger, and combustion chamber.


When you switch the furnace back on for the first time in months, you might notice a smell as the accumulated dust is burned off the heated parts inside. In this particular instance, the smell is actually completely normal. It’s not a safety hazard and it won’t damage your furnace, although it can be unpleasant for a few hours. If you leave the furnace running all day and the smell still doesn’t go away, then you might have a more serious problem and should contact your HVAC contractor as soon as possible.


The best way to avoid the build-up of dust in your furnace is to have it serviced shortly before the cold season starts. You should have an HVAC technician check out any appliances, including furnaces, once a year anyway, so it’s a good idea to schedule those tune-ups in September or October so the furnace is ready when the temperatures drop. The technician will make sure everything is still in good working order after the long break, as well as clean up any dust or grime that’s accumulated inside the unit while it was dormant. This prevents that nasty dust-burning smell when you switch the furnace on for the first time and ensures that everything is working the way it should.


Clogged Air Filter

If you’ve had your furnace on for a few hours, or the burning smell started during the cold season instead of on the very first day, then something more serious is happening inside the unit and you should shut it off until you can figure out what’s going on. One very common cause of a burning smell is a clogged or dirty air filter. The filter is one of the most important parts of any HVAC unit. It filters the air coming from the furnace, making sure no dirt or dust is floating in it before it’s transferred through the ducts into the rest of your home. Since furnaces aren’t actually pulling any air in from the outside, just heating up the same air over and over, it’s important that you have a way to clean the air so it stays fresh. With a properly-functioning air filter, your HVAC system is actually making your air cleaner as it changes the temperature.


However, just like any filter, the air filter in your furnace needs to be either cleaned or replaced fairly regularly. This is one of the most important things you can do to extend the lifespan of your furnace, but it’s something that many homeowners ignore or are unaware of. As a general rule, you should be either swapping or cleaning off the filter about once a month, although that depends on the type of filter you have in there. When you buy a new filter, the packaging should tell you how often it needs to be replaced – or cleaned, if it’s reusable.


If the filter is clogged, some of the dust and dirt it filters out of the air can fall back down into the furnace, landing on the heat exchanger. When that dust burns, it creates that same unpleasant smell. It can also be a fire hazard since the supply of dust isn’t limited. As the furnace keeps pulling air in, the filter will only get more and more clogged, and dust or pet hair can eventually start a fire inside the unit. Luckily, swapping the filter regularly will completely prevent this issue.


The other reason why a clogged air filter can create a burning smell has to do with the blower fan. Once the furnace has heated the air in the heat exchanger, the blower fan turns on and forces the warm air into the ducts, transferring it through the house. In order to reach the ducts, the air needs to go through the filter first. However, if the filter is clogged, then it can block the air from passing through, causing the house to warm up much more slowly. That in turn forces the blower fan to work harder and stay on for longer so it can push enough warm air through the clogged filter to heat your house. This can cause the motor inside the fan to overheat, creating a burning smell. An overheating blower motor can be a serious fire hazard and will also cause damage to the fan, potentially forcing you to replace it.


Electrical Issues

Another common cause of burning odors is an electrical issue inside the furnace. This is a much more serious concern than a clogged air filter and will require you to hire an HVAC technician to take a look at the issue. Electrical fires are one of the most frequent causes of house fires in the US, and it doesn’t take much to start a fire inside the furnace if you’re not careful. Electrical issues can come from several different root causes and it’s difficult to tell what’s going on unless you have some experience with HVAC repair, so your best bet is to just switch the whole system off until you can get it looked at.


One of the most frequent causes of electrical problems inside a furnace is a lack of maintenance. If you don’t stick to your schedule of yearly tune-ups, grime and dirt can build up inside the mechanisms of the unit. Just one dirty connection can be enough to spark a fire if you’re not careful, so it’s important to get your furnace serviced once a year. Regular maintenance can also prevent other electrical issues, like a worn-out capacitor or blower fan motor. These problems don’t usually come out of nowhere – they’re typically the result of a gradual breaking down process that can be spotted by a professional technician during a service appointment. A heads-up at the right time can prevent electrical failures inside the furnace.


Burning Plastic

If your furnace smells like burning plastic, there are a few reasons why that might be. The odor of burning plastic is particularly unpleasant and can even make you feel like choking or coughing, so it’s a good idea to get your furnace checked out as soon as possible. If you have small children in your household, a lost plastic toy is often the source of the smell. It would be difficult for a toy to end up inside the unit itself, but children will often drop them into the ducts by accident. Remove the registers from your vents and shine a flashlight inside to make sure there’s nothing in there. The metal ducts can easily heat up enough to melt a plastic toy, and the blower fan would force the burning plastic smell out through the vents into your home. If you do notice a melting toy or another plastic object, you can remove it yourself and see if the problem goes away.


Electrical problems can also create that acrid burning plastic smell. If your furnace is overheating, the plastic covers surrounding the wires can start to melt, giving off an unpleasant smell. A short can also cause this problem, or crossed wires. Either way, electrical issues aren’t really something that most people can fix by themselves. Electricity is extremely dangerous, especially when you’re messing around with damaged wires, and the risk of shocking yourself is pretty high. Unless you’re extremely confident in your own abilities as a DIY electrician, we’d highly recommend letting the professionals handle this particular issue. Just turn your HVAC system off and wait for a technician to arrive. If you want to be extra safe, you can switch off the fuse that supplies power to your furnace so you know no electricity is running through it.


Furnaces are mostly made of steel and aluminum since these metals are light, inexpensive, and highly resistant to heat. However, there are a few small parts here and there that are made of plastic. Normally, these small plastic pieces aren’t anywhere near the hottest parts of the furnace so they’re perfectly safe. If your furnace is overheating, however, then the increased warmth could be enough to melt the small plastic parts inside and create a burning plastic smell. This is most commonly caused by a malfunction in the heat exchanger. When the gas or oil burns in the combustion chamber, all the heat generated by the reaction is transferred through the heat exchanger into the air in the ducts. When the heat exchanger isn’t working properly, all that heat energy doesn’t have anywhere to go, so it just warms up the entire furnace, melting the plastic pieces inside.


The small plastic pieces in your furnace can also end up melting if they’re broken or shaken loose. Furnaces tend to vibrate as they operate, and that can sometimes cause little parts to break off. The humidifier nozzle, for example, is generally placed in a safe location above the heating element in your furnace. If the nozzle breaks or shakes loose, it can fall directly onto the heating element and burn up. The smell will generally go away once the piece has been completely melted, but you should still bring in an HVAC technician to check out the furnace and replace whatever broke off.


What to Do When My Santa Rosa Furnace Smells Like Burning

If you detect a burning odor coming from your furnace, your best bet is to let a professional take care of the situation for you. Allowing the furnace to continue running is risky for both you and the unit itself, so we don’t recommend just ignoring it. Here’s a quick rundown of what you should do if you notice a burning smell coming from your furnace:


  • First, turn off the furnace. If you want to be extra safe or if you believe that an electrical issue is the cause of the smell, you can always switch off the circuit as well from your fusebox. Either way, you should keep the furnace off until a technician is able to take a look and identify the problem, even if the weather is chilly. It’s better to be safe than sorry, and you don’t want to end up causing more serious damage to the unit or even starting a fire in your home.


  • You should also take a look at the unit itself to see if there are any visual signs of smoke or fire. Be careful, because the metal casing of the furnace could be extremely hot, especially if a broken heat exchanger is the source of the problem. If you do notice smoke or fire coming from inside the furnace, immediately call 911. If you have a fire extinguisher, you can try to put the fire out by yourself, but you should absolutely prioritize your own safety over the furnace. Firefighters can reach your house very quickly.


  • If you don’t notice any signs of an active fire and the furnace is cool enough that you can open it up, check the air filter. The filter is generally in the blower compartment in the bottom half of the furnace, although it can also sometimes be at the top by the air handler. You can check the instruction manual for the unit if you’re having trouble finding the filter. If the filter is dirty, clean it or replace it. You can try turning the furnace back on after cleaning the filter, but you should switch it off again if you still notice any burning smell.


  • If the odor smells like melting plastic, you can check the ducts for any toys or other plastic objects. Remove the registers from the vents and shine a flashlight into the ducts to look for any foreign objects. If you do see something melting in there, make sure you clean all traces of it before you turn the furnace back on. The fumes from melting plastic can be hazardous, so you want to be sure that all the plastic is gone from inside the ducts. If there’s nothing in the ducts, leave the furnace off.


  • If the furnace is cool enough that you can open the door, take a look inside for any signs of melting or burning parts. You don’t have to try taking it apart yourself, but it’s a good idea to inspect any visible areas to see if you can spot the source of the burning smell. Even if it’s not something you can fix by yourself, knowing where the heat damage is located will make the technician’s job a lot easier when they do arrive. Look for any signs of melting, burning, or scorching on all visible parts of the furnace.


  • Finally, get in touch with your HVAC technician. It’s always recommended that you have any HVAC-related problems diagnosed and addressed by a trained professional so there’s no risk of damage to the unit. If you need to file a claim with your insurance or use the warranty that came with your furnace to replace it with a new one, you’ll generally need documentation from a licensed HVAC technician confirming that the damage was accidental and not easily fixed. Furnaces are also pretty complicated, and it’s a lot safer to let a professional fix the problem instead of trying to handle it yourself. Even the most dedicated DIYers should defer to the pros when dealing with HVAC units, especially if there’s a risk of electrical issues inside the furnace.


Finding the Right Furnace Repair Company in Santa Rosa

If you live in Sonoma, Marin, or Napa counties and you need someone to take a look at your furnace, Valley Comfort Heating & Air is here to help. Our licensed HVAC technicians have plenty of experience handling anything your furnace or another HVAC unit might throw at them, so we’ll make sure the problem is taken care of. You can get in touch with us through our website here, visit our physical location in Santa Rosa, or give us a call at (707) 539-4533.


Keep in mind that the best way to prevent burning or melting in your furnace in the first place is to stay up to date with the unit’s regular maintenance. We recommend having any HVAC unit tuned up at least once a year, preferably right before the busy season starts. For a furnace, that means having someone take a look at it in October or November, shortly before the weather starts getting cold. Sticking to your regular service appointments will make sure your furnace stays clean while also allowing you to repair or replace any parts that might cause you a problem in the middle of the winter.