Where Are Those Air Conditioner Smells Coming From?

woman plugging nose due to smelly air conditioner

An air-conditioned room should ideally have no discernible smell, indicating that the cooling unit is functioning normally. Unfortunately, in some instances, an unpleasant or offensive odor may accompany the cool air when the air conditioner cycle kicks on. Such a scenario serves as a clear indication that there is a problem with the cooling system, and professional assistance should be sought immediately. This article outlines various air conditioner smells, their underlying causes, and the steps you can take to address the issue.

Explore Our HVAC Services Call To Schedule A Free, In-Home Estimate

What Is Causing That Air Conditioner Smell?

Continue reading to discover some of the typical smells that your air conditioner may generate.

Related Article: Common Air Conditioner Problems You May Face This Summer

Mold Smell

image of air conditioner mold

A common odor reported by homeowners with air conditioners is a musty smell resembling mold. This is often caused by water accumulation in the ducts, drain pan, or drip lines, creating a conducive environment for the spread and growth of mold, mildew, or fungus. The resulting foul odor can permeate the house.

Stale air in the home can also signal dirty air filters, particularly in hot and humid climates where moisture can accumulate and build up in the air conditioner’s filters. This can occur when the system has not been used for an extended period, and the stale air is circulated when the unit is turned on again.

To resolve these issues, regularly empty the drain pan. If the smell persists, contact an HVAC professional to inspect the air conditioner, ductwork, and lines. Water accumulation could also indicate a leak, requiring a thorough examination of the system to determine the root cause. Regular maintenance is critical to prevent such problems from arising with your central AC unit.

Call Today: (631) 667-3200

Related Article: How Does Your HVAC Affect Your Skin?

Cigarette Smoke Odor

If someone smokes tobacco in your home, the smoke particles can be drawn into the air conditioner and trapped in the air filter. This can occur every time someone smokes indoors. When the air conditioner is turned on, the smoke particles can become dislodged and mixed with the conditioned air, releasing cigarette smoke odor through the vents, even when no one is smoking.

Open a window when smoking indoors, or consider smoking outside. Regularly cleaning the air conditioner every 7 to 14 days by removing any dirt or particles from its surface can also help. Scheduling yearly air conditioner maintenance, ideally in the spring, can also aid in preventing the accumulation of smoke particles in the system.

Call To Make An Appointment

Related Article: Benefits Of A Whole-Home Dehumidifier

Burning Smell

image of electrical wires in an air conditioning system

If you detect a burning smell in your home, it may be due to a component of your air conditioner overheating and burning. A damaged cable, wire, or motor could be the culprit. If the air conditioner has not been used for an extended period, turning it on can expose dust buildup to high temperatures, leading to a burning smell. This odor should dissipate quickly, but if it persists, switch off the system immediately and contact a professional HVAC technician.

Avoid attempting DIY repairs on an air conditioner emitting a burning smell. Seek the services of a qualified HVAC technician instead.

Explore Our Air Conditioner Repair Services Call To Schedule A Free Consultation

Rotten Egg Smell 

When there is a dead animal in your air conditioning system, it can lead to a foul, rotten egg smell permeating throughout your home. As the body decomposes, gases are released, resulting in a pungent odor. Small animals, such as birds or rodents, may have gained access to your air conditioning unit and perished inside, causing the smell to spread throughout your home.

To address this, it is important to locate the dead animal in your system and ducts and carefully remove it. Afterward, the system should be sanitized thoroughly to eliminate any remaining traces. If the area is difficult to reach, contact a reliable HVAC technician with the necessary tools and experience to inspect, clean, and sanitize the system. They can also take steps to pest-proof the unit to prevent a recurrence of the problem.

Related Article: HVAC Allergies: How Your HVAC System Can Limit Seasonal Allergies

Gas Smell

Methyl mercaptan depicting natural gas leak

A gas smell is a cause for concern and should never be ignored because it may indicate a gas leak. The gas is odorless, so manufacturers add methyl mercaptan, which produces a foul smell like rotten cabbage, as a warning sign. Methyl mercaptan is an irritant that can cause skin and eye irritations, dizziness, nausea, headaches, and respiratory problems. Prolonged exposure to it can be fatal.

Turn off the gas supply right away if you suspect a gas leak, and ensure proper ventilation by opening windows. Evacuate your home and contact a reputable HVAC contractor without delay. Remember not to light anything because gas is easily ignitable in the presence of a spark or flame.

Call To Schedule An Appointment Read Our Reviews


When an air conditioner is malfunctioning, it may emit a range of smells. While some odors may not be harmful, others may indicate significant and potentially life-threatening issues. Some smells can be addressed by cleaning or replacing the filter; others require the attention of an HVAC specialist. Do not ignore any smells emanating from your air conditioner. Addressing the problem right away will typically prevent health problems and avoid the need for costly repairs or replacements in the future.

Get Started - Call Hart Home Comfort Today

Related Article: How To Deal With HVAC Ductwork Noise

Call Hart Home Comfort For All Of Your HVAC Requirements


Hart Home Comfort is a trusted provider of high-quality HVAC services in Nassau County, Suffolk County, and Queens, New York. Our team consists of professionally certified technicians equipped to handle all your heating and cooling requirements. Whether you require air conditioner tune-ups, furnace repairs, mini-split installations, or boiler replacements, we have the expertise to safely, correctly, and promptly service any make and model.

We take pride in offering the most cost-effective and competitive rates in the area without compromising quality. Our maintenance services can help you improve your indoor air quality, comfort, and energy efficiency. If you need an HVAC repair or replacement system, our friendly techs can recommend the best and most budget-friendly solutions. We prioritize your satisfaction, which is why all our services are guaranteed. To schedule a service appointment, call Hart Home Comfort today, and take advantage of our free, in-home estimates.

Call Now: (631) 667-3200 Explore Our Case Studies

For any questions about what Hart Home Comfort can do for you, give us a call today. Click here to contact us now or call us at (631) 667-3200 to find out more! Click the link to view our service area.