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Homeowner holding nose due to smell in home from HVAC system

Say Goodbye to that Musty Smell in House!

Have you noticed a musty smell in house? You may find yourself wondering if your home always smelled that way, or when the damp scent started to permeate throughout your house. While it's unlikely you moved into a musty house to begin with, it can be difficult to track down what's causing unpleasant odors to waft through your walls.

Chances are, the likely culprit was your HVAC system. Since the system helps purity the air you breathe and is responsible for your home's air quality, when there is an issue your entire house can be affected.

If you take a look at your air conditioner or furnace and notice a musty smell—or another smell all together—contact your local Aire Serv pros. Our team of experts possess the skills needed to diagnose and solve a range of HVAC related problems—from a water leak in your AC unit to issues with filters and ventilation fans. We've got it covered.

To learn more about why your house may smell musty and how your HVAC system impacts your home's indoor air quality, keep reading.

How Does My HVAC System Impact Air Quality?

Since your HVAC system either expels cool or warm air, it has a big impact on your home's air quality. That's one of the reasons why both furnaces and air conditioning units have filters. While these filters help keep debris such as dust and dander from coating the various parts that make your HVAC system run, they also reduce contaminants in the air you breathe.

Furthermore, if there is an issue with your HVAC system—such as moldy vents or excess moisture in an AC unit—it could cause bad smells to propagate. We've broken it down so you know which of these bad smells come from your AC unit, and which come from your furnace.

Help! My AC is Making My House Smell Musty

There are many benefits to having an AC unit—including keeping your home at a comfortable temperature all year long, removing humidity and improving air quality. However, issues with your AC can cause a musty smell in your house. A few issues that cause a musty smell include:

Excess Moisture in Air Ducts

A couple of common causes of excess moisture that accumulates inside ducts and vents include high humidity levels or a drainage leak. Moisture tends to cause mold spores and mildew to develop. If you notice a musty smell when you turn on the AC, it could be that moisture in the duct work has caused mold growth.

Toxic mold exposure can cause a wide range of respiratory and health issues—especially if any of your family members are seniors or have a respiratory illness like asthma. Subsequently, should you notice a musty odor while using your HVAC system, it's important to call a professional technician to clean the ducts and vents and repair any damage to prevent future musty smells and mold growth.

Frozen Evaporator Coils and Dirty Filters

A clean filter is quintessential to a properly working AC unit. When the filter gets congested with dust and debris, it impedes proper air flow. In turn, this causes water drops from humid indoor air to collect on the machine's evaporator coils. Subsequently, the coils freeze as the AC unit works to cool air. When the coils are frozen, the machine will stop working correctly. This causes humidity to increase in your home, possibly causing a musty smell. Fortunately, this issue can be easily remedied by swapping out or cleaning dirty filters every one to two months.

A Full Drain Pan

An AC unit's drip pan catches water droplets that are removed from humid air by the machine. It's natural for this part of the unit to wear over time, meaning it will start to function less efficiently. As we mentioned earlier, where there is moisture, mold can grow. This is true of your drain pan. An inefficient drip pan can accumulate mold, creating a musty odor you'll begin to notice each time the machine is operating.

Blocked Condensate Line

Unfortunately, the condensate line is one of the most likely places where mold, mildew and sludge will begin to build up—causing a musty odor to permeate through your home. The condensate line is a small pipe next to the condenser unit—which is the outdoor part of your AV machine. The line is responsible for draining water from the drip pan to your landscaping or storm drain. When covered in mold, mildew or other debris, these leaky pipes can clog and lead to musty smells in your house.

The good news is, this issue can be prevented with regular cleanings—and cleaning the condenser line is fairly straightforward. Simply follow these instructions:

  • Turn off the AC unit at the thermostat and breaker panel.

  • Remove the condenser line.

  • Pour a cleaning solution or white vinegar mixed with warm water into the pipe.

  • Let the cleaning solution sit for 30 minutes.

  • Rinse thoroughly.

  • Reattach to the condenser unit.

  • Turn the unit back on.

Improperly Sized Unit

Your HVAC system needs to be the correct size for your home, or it won't work properly. When it's too big, air gets cycled too quickly. This means it's not being dehumidified completely, resulting in excess moisture in your home. This can lead to mold growth and a musty smell that's difficult to get rid of—especially if mildew and mold are growing in your drywall. If you're concerned that your AC system is too big or too small for your home, call your local Aire Serv technician. We'll help you find an appropriately sized machine—and get rid of unwanted odors in the process.

SOS! A Strange Smell is Coming from My Furnace

While a musty smell in your house is more likely going to be because of an issue with your AC unit, this is not always the case. Also, there are a few other lingering odors that can be attributed to a problem with your heating system.

Musty or Mildew Odor

Have you noticed a moldy odor when your furnace starts up? If you have a split system that's connected to your AC system, then any musty smells that are developing in the AC can also be spread through your heater. Likewise, clogged and dirty filters can create a musty odor. Just like how you need to regularly swap out filters in your AC to prevent mildew growth, you also need to change the ones in your furnace roughly once a month—or according to the manufacturer's instructions.

Burnt Dust

Depending on where you live, you might not use your furnace all year round. This means that as the cold weather starts, you may fire up your furnace for the first time and notice a strange scent. Just as unused items can gather dust in your home, dust also collects on your furnace while it's not in use. The first time you turn on your heater, some of this dust might get burned away—causing that foul odor.

The good news is, this household smell is nothing to worry about. After a few heating cycles, the odor will clear up on its own. If the problem persists, you may want to consider hiring a professional HVAC technician to clean the machine and perform a routine maintenance check.

Oily Smells

Do you have an oil-fired furnace? Then from time to time you may smell oil. Just like how a car can spill oil occasionally, so can your furnace. If oil is spilled, say from refueling your machine, the scent may linger for a few days before it dissipates.

However, if you smell oil and your machine wasn't recently refueled, then it's more likely an oil leak has occurred. In this case, it's very important to call a professional to carefully inspect your furnace for leaks and other issues. For instance, a dirty or malfunctioning burner can also produce unpleasant oily odors.

Noxious Fumes

Noxious exhaust can get stuck in your home if you have a partially or completely blocked exhaust chimney. A blockage can also cause carbon monoxide to build-up in your home. Although you can't smell or taste carbon monoxide, this gas can cause serious illness and even death. That's why it's essential to clean your exhaust system regularly, and ensure you have working carbon monoxide detectors—especially near bedrooms.

Rotten Eggs

Likely the most common smell homeowners know to watch for, rotten egg odors are cause for concern. Natural gas and propane are odorless and colorless in their natural states. This makes them almost impossible to detect in the event of a leak. However, knowing this, propane and natural gas supplies add methyl mercaptan, an organic compound, into the gases. This compound creates a very powerful scent similar to rotten eggs. If you notice rotten eggs in your home, then you know there is a gas leak.

Should this happen, turn your heater off immediately and open a window—even if it's cold outside. It's important to properly ventilate your space so the gas gets out. Then, exit your home and call a local gas company or fire department to shut off the gas supply and find the leak. If it's discovered that your furnace is the problem, a qualified HVAC technician will be able to make the necessary repairs.

Metallic Smells

If you smell an acrid or metallic odor, then it's possible the electric wiring in your furnace is burning. Electric shorts caused by damaged wiring can create sparks and melt wiring insulators. It's also important to note that since most of your furnace's parts are made of metal, they can give off a metallic odor when overheating. Any time you smell metal coming from your heater, turn it off and call an HVAC technician right away. The damage will worsen if left alone.

Burning Plastic

Similar to metallic smells, if you notice the scent of burning plastic, then one of the plastic parts in your furnace is overheating. Likewise, heat-damaged circuit boards may also give off the smell of burning plastic. This is also a situation where a heater repair expert should be called right away to assess and repair the damage.

Trust the Experts at Aire Serv for Musty Smell Removal!

If you have a musty-smelling house, notice a moldy odor when you turn on the AC or smell something foul coming from the furnace, call your local Aire Serv technician right away. Bad smells are not only unpleasant, but may also indicate a serious problem that could result in further damage or health issues for you and your family.

Keep your home safe and comfortable—and get rid of that musty smell in your house—by trusting the experts at Aire Serv. Across the country, our technicians are highly trained, experienced and hard-working. We have the industry knowledge to solve a wide range of HVAC problems, and are always happy to take your call. Customer service is one of our top priorities. We know how stressful having an issue with your HVAC system can be, which is why we work hard to provide courteous and diligent service to try and relieve some of that stress.

To stop your house from smelling musty today, or to inquire about your Aire Serv's various HVAC services, get in touch today.