Warm weather is right around the corner, and you can’t wait to turn the air-conditioning back on. But you may notice some strange HVAC smells emanating from your system.

These HVAC smells are a pain, and you should always check with a technician to rule out more serious problems. Here are the main culprits causing those nasty odors drifting into your home.

Rotten Eggs

A rotten egg smell coming from the HVAC system could be a natural gas leak. The reasons for a natural gas leak are varied — some are serious, while others can be easily fixed by calling a professional.

Natural gas is odorless, but gas companies add a distinct smell to it so that people can detect it if there is a leak. If you see or hear any signs of leakage, contact your local utility company and the fire department immediately.
A licensed HVAC technician can also help prevent leaks before they become serious problems by performing routine maintenance on your heating system throughout the year.


There are many reasons why your HVAC unit may be emitting an unpleasant odor, from a clogged drain line to a dirty air filter. But there’s one thing that can contribute to an unwanted smell in any home, and that’s sewage.

The following are some common problems that could cause sewage smells in your HVAC system:
  • Clogged drain lines – Sewer gas can permeate through your home’s drains and into the HVAC system if the pipes are clogged or damaged. If this happens, the gas will enter your home and cause foul odors.
  • Dirty air filters – If you don’t clean your air filters regularly, they will become clogged with dust and other pollutants that emit foul sewer-like smells.
  • Dirty coils/blower motor – Mold or mildew growth on the coils or blower motor will likely emit odors similar to a sewage smell.
  • A dead animal in the vents – rodents often climb into vents in the colder months to keep warm. If they die and decompose, they leave a smell similar to sewerage in your system.

Contact a professional immediately if a sewer smell is coming from your HVAC system. Methane gas can harm your health.

Dirty Socks

Dirty sock smell coming from the HVAC? The likely cause is mold and mildew on the evaporator coil.

The evaporator coil is often found inside your furnace or air conditioner. It’s the part of the system that cools the air before it circulates through your home. The coil is made up of fins wrapped around a metal core. As warm air flows through these fins, moisture condenses on them and drips down into a pan underneath. When not used in the winter, the moisture leads to mold growth.

Mold and mildew can be harmful to health if inhaled. So, it’s always best to contact an HVAC technician immediately for an HVAC clean-up.

You can prevent the growth of mold and mildew by booking regular HVAC tune-ups throughout the year.


A musty odor in your HVAC system can come from several sources. The most common cause is mold and mildew growing on the coils and ducts. This occurs because the system isn’t being cleaned regularly.

Another source of mold and mildew is dust and dirt that builds up inside the unit, which can lead to a musty smell.

The best way to prevent this problem is to have your system cleaned regularly. Call your local HVAC company and ask them to come to inspect your unit. They will be able to identify any issues with the unit and make any necessary repairs before they become a problem later down the road.

Electrical Odors

Electrical odors can be caused by several different factors. The most common cause is a loose connection or poor electrical connection within the HVAC system. This can be caused by improper installation, an improperly installed filter, or a filter that has been damaged by dust or dirt.

If you are experiencing electrical odors coming from your HVAC system, it is essential to have this checked out by a professional technician. An improper connection could lead to electrical arcing or even fire in extreme cases if left unattended.


Most people are familiar with the smell of oil or burning rubber from their heating and air conditioning systems. This is usually a sign that it’s time for an HVAC service call.

If you smell a burning odor from your HVAC unit, it means something is wrong with your system’s lubrication process. In most cases, either you need to have your unit serviced, or there’s a leak somewhere in its inner workings that needs repairing.

Struggling to find the source of your HVAC smells? Contact the HVAC experts at JW Plumbing, Heating and Air to get rid of those annoying odors.

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