What’s that smell? While some odors are completely normal, others can be a good indicator of a larger issue with your HVAC system. Below we will walk you through the common causes for odors, as well as the smells to watch for, and what they might mean for you and your home. 

First, let’s go over the common causes of furnace/AC odors. 

• Dirty air filters

 Dirty air filters feature a collection of dirt, dander, dust, and other biological contaminants. All of these play a large role in obstructing the airflow through your unit, decreasing the overall efficiency of your HVAC unit. But along with this, it’s also important to note that dirty air filters can and often will lead to unpleasant odors drifting through the air in your home. For a visual, clean, conditioned air is flowing through your furnace, passes through the unclean filter, and while doing so, transfers the dirt, dander, dust and other contaminants throughout your entire home. It’s important to keep up with routine maintenance and air filter changes to avoid this from happening. 

• Cracked heat exchanger

Normal wear and tear on your unit can cause your heat exchanger to crack or become faulty. This happens because the heat exchanger holds the sole responsibility of heating the air in your home to your desired temperature before distributing it throughout. As time passes, this wear and tear can cause your heat exchanger to crack. When this happens, you more than likely will not be able to smell something chemical in your home when your heater is on. It’s vital to replace this part as soon as possible to prevent any further damages to your unit, home, or family.  

• Dampness 

If your furnace is located in a cool dark area, you may notice that you smell a musty odor when it is turned on and running. Implementing waterproofing techniques could help. 

• Mold/Mildew growth 

Again, we see this issue in places that are moisture-filled, dark, and optimal conditions for mold/mildew growths. 

• Overheating 

This is often a product of an electrical issue. 

• Ventilation issues

This could go hand in hand with unclean air filters. Often we see ventilation issues when there are pets occupying the home. This happens because pet dander is sucked up and ran throughout your AC unit.  

• Blockages 

Blockages can vary, but some of the most common reasons are general build-up or deceased rodent(s) located inside the ventilation system. 

Now, what’s that smell? And what does it mean? 

Being a homeowner, it’s naturally important to know what’s going on with your home. You may occasionally recognize some of these smells, and when you do, it’s important to know what they might mean for you. 

Musty or Moldy Odors 

This is one of the more common smells homeowners have reported. And while mold and mildew don’t pose a huge risk to your HVAC equipment, it does pose a large risk to your personal safety and health. It’s important to have an HVAC provider come and inspect your unit, and check it for condensation issues, drainage issues, as well as your ductwork. The musty, or moldy odor you are smelling is often a result of bacteria growth on the coils in your air conditioner or heat pump. A simple tune-up should fix the problem. 

Burning Odor

Ah, the first time turning on your furnace after a long summer. The faint odor of a hot iron permeates through your home, a sign that your heater is on, and working. But what if that smell doesn’t go away within a few moments after turning it on? This could be a normal reaction to your heat exchanger burning off dust and dander that had been gathered over time. This could also be a sign of a more serious problem, such as an electrical issue. If you notice that the smell isn’t going away, check your air filters. If they are dirty, it’s likely that this is causing your unit to become clogged, which restricts your airflow and will cause an electrical resistance, causing your heater to overheat. If you suspect a more serious issue than just a clogged air filter, it’s important to turn the power off, and contact an HVAC professional immediately. Never attempt to forgo any electrical work to your HVAC unit. 

Acetone Odor 

Is that fingernail polish remover I smell? Afraid not, it’s more likely that you have a refrigerant leak. This happens often in systems that are older or have not been properly maintained over time. Along with reducing the effectiveness of your unit, it can also be hazardous, as the fumes that are released into the air are highly flammable in nature. It’s important to get this issue fixed as soon as possible. Your certified HVAC technician will find the leak, repair the leak, and tip you off on the refrigerant. 

Rotten Egg Odor 

A smell, nobody likes. The very common “rotten egg odor” is also known as natural gas. This happens when you experience a leak inside your system. Natural gas is actually biologically odorless. What gives natural gas the funky rotten smell is a chemical called “Mercaptan”, which is added to natural gas for consumers to know that there is a leak. Otherwise, this would be a silent killer. It’s important that you turn off the gas as soon as you recognize this smell. Open all your windows, and doors and call your local HVAC professionals to inspect your home and equipment. While you are waiting, it’s important not to use any electronics, or cause a spark of any kind. This includes open flames, which can cause a mass explosion. It’s advisable to remove yourself from the home and area until the problem has been fixed.

Urine Odor 

Do you smell something similar to urine throughout your house when your unit is running? That could be because of a rodent infestation. It’s very common for mice to nest in or around your HVAC equipment as well as your ductwork. Obviously, if this is their new living quarters, they will be nesting, urinating, and defecating inside of your equipment or ductwork. The best way to solve this issue is to find where they are and remove them. After the mice have been addressed, it’s important to install an air filtration system for your home, and give your ducts a healthy cleaning. 

Stale Odor 

This is one of the more popular smells that are reported. This is usually a very common issue for many homeowners. The stale odor that you smell is often from a ventilation issue. And while having great insulation, along with properly installed doors, and windows is usually a great thing, this only adds to the smell. Still stale? Open your windows on a frequent basis to allow fresh air to flow through your home. 

Decaying Odor

This one is roughly self-explanatory. If you smell something decaying coming through your vents when turning on your system, it’s likely that something is deceased inside your unit. Removing the problem, and giving your unit a good clean should remove this smell.  

“Dirty Sock Syndrome”

Essentially this means that when moisture, dust, and debris build up on your AC system evaporator coils, it’s a grand invitation for bacteria and mold to breed rapidly. This causes a foul-smelling odor close to the smell of mold or mildew. 

Beware of the Silent killers, Natural gas leaks. 

This has been found in furnaces that are powered by natural gas. This is a serious problem, and you should leave your residence immediately. It’s important to remember not to operate anything that can cause a spark to occur. Such as but not limited to; turning on lights, using a cell phone, lighting a candle, turning on a stove, or any appliances for that matter. Get to a safe location and call 911. A crew will likely come to check on the status of your home and locate the source of the smell. Once the area is safe, you may return, but only under the advice of a professional or emergency services personnel. 

As with anything, it’s advisable to seek the help of a professional HVAC technician to assess your unit for something potentially more serious. Contact a member of our team today for inspection and service.