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45 thoughts on “6 Toxic Air Conditioning Smells and What They Mean”

1. We have a portable air conditioner until 12 BTU when it’s on it draws the smell of creditor in the house.. we have a wood forced air furnace.
   How ca we solve the problem

   Many thanks

   Jen

   1. Hi Jen,

      Unfortunately, we do not service portable AC units. We recommend contacting an HVAC contractor in your area who does.

   2. Hi if ac is off can u cover the vents do u can’t smell it

2. My window A/C unit smells like the inside of my freezer. Is it the Freon??

   1. Hi Dee,

      We actually don’t work on window AC units. We recommend calling other HVAC companies in your area to see who does.

3. I have an odor in my home that smells like sulfur and sometimes the odor is like a ginger with onion smell, cause at times it causes my eyes to burn, occasionally nose runs a little, it also makes me cough every now and then. The smell gets really bad when I run my hvac. It’s a central unit. Some when I run my hot water seems like it’s coming through my drains,had my water company to check things out it’s not the problem.

   1. Hi Mary,

      Your HVAC system smelling of rotten eggs or sulfur most likely indicates a natural gas leak. Although on its own, natural gas is odorless, most utility providers add the aroma to alert people of a dangerous leak. Don’t take this lightly. If you smell a rotten-egg-like odor in your home, natural gas is likely the culprit, and immediate inspection is a must. While low level exposure is not hazardous to your health, high levels reduce oxygen in the blood, and can lead to loss of consciousness and death. Gas is also highly flammable and explosive, resulting in dozens of deaths each year. If you notice this smell, open the windows to your home right away, get out of the house immediately, then call the gas company.

4. Musty heat smell from ac unit an Ahri unit rap 13

   1. Hi Mick,

      An air conditioner smells like mildew or mold is probably the most common symptom of central HVAC systems. When the air conditioning is running, there is a lot of condensation within the unit. When the moisture doesn’t drain properly, it can escape into the ducts and create mold. Finding where the mold buildup is and getting it cleaned up will solve the problem. An HVAC repair technician has the knowledge to handle the problem and ensure that it doesn’t occur again. Note: Mold and mildew smells are not serious problems with the unit, but the poor air quality does increase the risk of respiratory infections in both children and adults. You can still use the unit while you’re waiting for repairs, but you shouldn’t put it off for the sake of your family’s health.

5. Why does my window air conditioner smell like gas??

   1. Hi Lisa,

      We do not work on window ACs. However, if it is smelling like gas we recommend that you turn it off to protect your healthy until you have a professional come out to inspect it.

   2. My ac smelt like a gassy smell chemical of some sort i called matenace and told them i was smelling something… He said nothing he can do tonight just shut it off, Be there by 8am. i felt kinda disoriented..my friend shared this ad to me and it helped me feel so much better you really have the answers and i thank you so much !! Marie Dillon youngstown ohio….. T Y.

      1. Hi Marie,

         We are glad you found this article helpful and hope maintenance was able to fix the situation for you. If you do smell gas again, turn off your HVAC system in order to protect your health until a professional can look at it.

6. My home smells like a car or vehicle with a really bad exhaust leak. Its really strong like oil or fuel burning thru an exhaust leak on a vehicle. What could it be??

   1. Hi Shelly,

      Even in HVAC systems not powered by gas, exhaust fumes can still result if fluids leak from essential components. To avoid a dangerous situation, have your system professionally assessed. Burning oil and other fluids can release large amounts of toxic gases, different in chemical makeup than in natural, liquid form. These particulates can be hazardous to your health, depleting oxygen and resulting in an array of health issues.

   2. My AC unit smells like the tip of a match. The red part. Not sure why or what but is this ok to run until the smell burns off? Or will it?

      1. Hi Nickie,

         Is this the first time using your unit in a while? If so, we recommend letting it run for 20-30 minutes to see if the smell goes away. If it does go away, it probably was dust on your unit burning off. However if the smell continues please contact your local HVAC company so a professional technician can assess your system. If you are in the Vancouver, WA or North Portland, OR area we would be happy to help if the smell persists!

7. After a new furnace an air conditioner install my house smells like moth balls!

   1. When you say it smells moth balls do you mean that it smells moldy or musty? If so, an air conditioner smells like mildew or mold is probably the most common symptom of central HVAC systems. When the air conditioning is running, there is a lot of condensation within the unit. When the moisture doesn’t drain properly, it can escape into the ducts and create mold. Finding where the mold buildup is and getting it cleaned up will solve the problem. An HVAC repair technician has the knowledge to handle the problem and ensure that it doesn’t occur again. Note: Mold and mildew smells are not serious problems with the unit, but the poor air quality does increase the risk of respiratory infections in both children and adults. You can still use the unit while you’re waiting for repairs, but you shouldn’t put it off for the sake of your family’s health.

   2. Yes..mine is smelling like mothballs as well. What is that?

      1. Hi Sandy May, Sounds like you have a similar situation to Lukie. When you say it smells moth balls do you mean that it smells moldy or musty? If so, an air conditioner smells like mildew or mold is probably the most common symptom of central HVAC systems. When the air conditioning is running, there is a lot of condensation within the unit. When the moisture doesn’t drain properly, it can escape into the ducts and create mold. Finding where the mold buildup is and getting it cleaned up will solve the problem. An HVAC repair technician has the knowledge to handle the problem and ensure that it doesn’t occur again. Note: Mold and mildew smells are not serious problems with the unit, but the poor air quality does increase the risk of respiratory infections in both children and adults. You can still use the unit while you’re waiting for repairs, but you shouldn’t put it off for the sake of your family’s health.

8. Hello,
   For well over (3) months, there has been a foul odor ( I would describe as a dead animal) coming from my bedroom AC vent. It was strongest (3) mos ago, for the first (2) days it was unbearable. The latter few mos, it would come and go. I have removed the vent and inspected for animals but found nothing? Oddly, even at its strongest, it is unnoticeable once the AC is running? Any suggestions? Thanks

   1. That is an unusual situation. Normally when our customers smell something like that there is a dead animal within the duct work. Where do you live? If you are in the Vancouver, WA and/or North Portland, OR area we can have one of our technicians come out to inspect your system.

9. Hi
   There is a odor coming from my Air Conditioner Unit, that smells like musty or someone’s butt that hasn’t washed! I have been smelling it for at least a week or more! I am a asthmatic it causes me to cough and I feel nauseous at times. How do I solve this problem! Upon turning it off I looked inside I do see mold spots.

   1. An air conditioner smells like mildew or mold is probably the most common symptom of central HVAC systems. When the air conditioning is running, there is a lot of condensation within the unit. When the moisture doesn’t drain properly, it can escape into the ducts and create mold. Finding where the mold buildup is and getting it cleaned up will solve the problem. An HVAC repair technician has the knowledge to handle the problem and ensure that it doesn’t occur again. It’s also important to keep up on annual maintenances of your system in order to keep the indoor and outdoor units clean of mold and dirt.

10. There is like a rubber smell or electrical coming from the vent. Was checked and nothing was found

    1. Electrical odors could indicate a mechanical problem with your AC fan or compressor, wiring issues, or electrical component failure. Made with a variety of metals and chemicals, prolonged exposure to these fumes is not healthy. The first few times the unit kicks on, it may emit a burning odor that can smell electrical and dusty, give it 20 to 30 minutes and see if the smell dissipates. If it does, it probably was just the dust burning off. If it continues, contact a professional HVAC technician to check out the problem and make repairs. An electrical odor typically is a problem within the motor or the wiring. Attempting to fix either of these items can result in severe injuries.

11. We had a new central air unit and furnace installed today. I keep smelling something. Its aerosol type smell. Kind of like spray paint.

    1. Hi Patti,

       I would recommend calling the HVAC company that installed your new central air and furnace and explain what you are smelling. Since you just had it installed, it should be free for them to come out and make sure everything is ok with your system.

    2. That is exactly what I smell! We just had it replaced about an hour ago and the smell is making me extremely nauseous ?

12. I have had a gas smell for several months. Called gas person in February. It ended up being my gas stove/oven per the gas company. Now that the air conditioner on, I still smell a gas smell or paint thinner and I hear an airy sound as well. Have not located the source of the airy sound. Gas people said that I am hearing the gas travel up the wall. Tested; no gas indicated. Called heating/air to do maintenance and to check as well. New roofing in the community. Could this be it. Can smell back draft from neighbor’s vehicle. Which is the problem or all?

    1. Hi JJ,

       When the HVAC company came out to do the maintenance, what did they have to say about the gas smell and airy sound that you have been hearing?

       1. They said it was the upstairs neighbor’s air conditioner. As of this week, the gas people found out that the gas smell was the gas meter and fumes from a stove that I had not cooked on in a month. I still have the air sound. Do you think it is air from a pipe that needs fixing or insulation or something stuck in the vent?

          1. It’s difficult to determine the exact cause of the air sound without investigating it in person, but I did speak to a technician and they think insulation would help.

13. my new 4 ton heat pump began emitting a strong metallic like odor, like aluminum in ac mode. it doesn’t smell at all in heat mode. my evap coil is aluminum. is that what i’m smelling? my old unit had copper coil and i smelled nothing.

    1. Hi James,

       I checked with one of our service technicians. He said that normally that type of smell is emitted during heating mode. Your unit’s indoor coil may be leaking refrigerant, which can give off a metallic smell. We recommend having the company who installed your heat pump come out to take a look. If you are in the Vancouver, WA and/or North Portland, OR area we would be happy to help!

14. Hi, my air conditioner had recently started to leak water, at first it was small leaks, but then in day 2 the leaks got more severe, to the point where at certain points it was dripping water, i woke up today to a small puddle on the floor under the ac unit (split). There werent any odors inside the room, but i noticed when i smelled the area of the floor where the puddle had been that it smelled like chemicals, and the puddle had a bit of a pinkish hue to it, although otherwise i have not seen the pink hue. The AC still cools as normal, but i have refrained from using it after that. What could that smell be? and is it leaking water or something else.

    1. Hi Maiz,

       I spoke with one of our service technicians. He said that it sounds like water is leaking from your system either because a condensate line is clogged or the copper line isn’t insulated and it’s dripping from there. You would need to get a service technician out to look at your equipment in order to determine the cause of the smell and to stop the water from continuing to leak. If you are in the Vancouver, WA or North Portland area we would be happy to help by sending a technician out to take a look.

15. james cox on july 10 wrote that his 4 ton aluminum coil ac gave off an aluminum smell. my new aluminum coil 4 ton carrier heat pump does the exact same thing. metallic smell in ac, no smell in heat. my house cools really fast and i’ve had this unit for a year with no recharges. what’s going on here? just hypersensitive to aluminum sell?

    1. Hi Adriaan,

       It sounds like your system is running well and most likely doesn’t have a leak. I spoke with our Service Manager and he thought it might not even be the coil causing the smell. Often times IAQ products emit ozone which can smell metallic. Do you have any IAQ products as a part of your HVAC system? In order to further diagnose the issue, we would recommend having an HVAC company come out to take a look at it. It’s difficult to fully determine the cause of the smell without being onsite.

16. We have 1-yr old central AC unit. It emits smell when the fan is constantly on and AC is off. When the AC turns on the smell gradually disappears. When the temperature drops to the needed one, the AC turns off and the smell reappears again. The smell is quite strong. Not the mold or musty for sure. And not the rotten eggs either. Some sort of “technical” smell. There is no smell when the fan is constantly on and the unit in the heating mode. The reason of keeping the fan constantly on during the air-conditioning hours is to prevent building mold inside the system.

    1. Hi Vlad,

       Could you explain the “technical” smell in a little more detail? Is it an electrical smell? If it is an electrical smell, it could mean you have a mechanical problem with your AC fan or compressor, wiring issues or electrical component failure. Exposure to this smell/fumes can be very unhealthy. We recommend having a local trained HVAC technician come out to your home and inspect your unit. If you are located in Vancouver, WA or Portland, OR (our service area) we would be happy to send someone out.

       1. Thanks for reply. The smell is vaguely comparable with the smell of burning transformer coils, but not exactly. I know the smell of burning transformer very well. It’s different. The same smell appeared in my previous house from AC unit after living there for 10 years. A year later I moved. And now the same smell at the new place from a brand new AC unit. Amazing. I’m going to ask the guy who installed it to drop by and chek the unit when the pandemic is over.

17. There is a paint thinner smell coming from my AC vents in my apartment. I called the manager, but her response was not promising. Is it safe to stay in my apartment?

    1. Hi Meghan,

       We would recommend getting a professional HVAC technician out to asses your system right away. Your AC does use an assortment of chemicals in order to run; it sounds like your AC could be malfunctioning (hence the smell) and needing repair. If you are in the Vancouver, WA and/or North Portland, OR area we would be happy to help! Our phone number is 360-695-6500.

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