Why Does My Air Conditioner Smell Like Rotten Eggs & What To Do?

We all can recall the smell of rotten eggs, which is very unpleasant. But once you find your air conditioner at home blows air that has such a smell, what to do with it?

In most cases, the odor of rotten eggs in your air conditioner is caused by a natural gas leak, sewer gas, or dead animals. You must resolve it as soon as possible, regardless of the cause.

In this post, I will go over each cause and solution of an air conditioner smelling like rotten eggs. It should be helpful if you have no idea how to handle this situation. 

Causes of an air conditioner smelling like rotten eggs

While I answered this question shortly at the beginning, there are more details you need to know. The smell of rotten eggs can be a sign of danger, and you need to exercise caution. 

Natural gas leak

why ac smells like rotten eggs

On hot summer days, we like to keep our air conditioning on all the time. If you come home and the room smells like rotten eggs, there is probably a gas leak.

The smell of rotten eggs is caused by a specific component called sulfur. If such a component is introduced into your home’s air conditioning system, it can cause the ac system to emit a sulfur odor.

The natural gas doesn’t have any odor initially. Since inhaling natural gas can lead to fatigue, nausea, loss of consciousness, or even death, and the gas is flammable, gas companies add a smelly chemical to make people detect the danger easily.

The chemical is mercaptan, an organic gas composed of carbon, hydrogen, and sulfur. You see, it contains sulfur, so it will release a smell of rotten eggs. But this chemical is harmless, even though it smells.

Therefore, when the gas leaks, it will circulate into your house in the ac system, and the rotten egg smell will remind you to take action immediately. (More on that later)

Sewer gas leak

Sewer gas exists in the sewer system, which comes from the breakdown of human waste and food. If it gets into your home’s air conditioner system through the air ducts by accident, your ac will start to blow air with a smell of rotten eggs. 

Sewer gas may not be as toxic as natural gas at low levels; however, it can still pose health risks to you, such as headaches, nausea, and poor concentration

Sewer gas composes of a few different gases, like ammonia, carbon dioxide, and hydrogen sulfide. It has a sulfuric odor mainly because it contains hydrogen sulfide.

Normally, the sewer gas will be kept in the plumbing system and will not get into the room. However, when there is a leak, it will seep into the ac system, leaving your house with an unpleasant odor.

Dead animal

This is probably the last thing you want to see, but it can happen, especially with a central air conditioner.

Small animals, such as mice, prefer warm environments, making the ductwork an ideal home for them. They may become trapped and die if they enter the duct.

Decaying animals can give off rotten egg odor, which can get into your house through the air conditioning system. Note that dead animal can also make your ac system smells like pee or vinegar.

How to get the rotten egg smell out of your air conditioner?

Because the rotten egg smell coming from the ac often indicates a gas leak, you should proceed with caution. Here’s what you should do.

Open the window and leave the house

Because natural gas can make you lose consciousness and die, you should go away from it as soon as possible. 

Open the windows in your house to allow the gas to be expelled. Don’t use equipment that can trigger a fire and leave the house. If possible, turn off the gas supply if you know where it is. 

Make sure everyone in your house is outside, and call the local fire department and gas supplier. 

Please don’t try to fix the leak on your own, which could kill you and your family members.

Hire a plumber to examine the leak in the plumbing system

The rotten egg smell in sewage can be quite unpleasant. It may be difficult to pinpoint the source of the problem because anything in the plumbing system, such as a loose toilet or clogged air vents, could be the culprit.

Rather than taking the time to locate the leak, you should hire a plumber to detect and repair the problem.

Take out the corpse

If none of the methods work, the foul odor should come from the dead animal in the ductwork. 

You can wear a glove to take it out if the dead body is near the air vent. If not, an HVAC expert should get the job done. 

How to prevent the smell of rotten eggs in your AC?

how to prevent smell of rotten eggs in ac

Strictly speaking, the rotten egg smell in the home’s air conditioner doesn’t come from the internal part of the ac. Instead, the unpleasant smell is caused by other systems and then dispersed all over the place through your ac.

As a result, you should have your HVAC system, plumbing system, and gas piping system serviced on a regular basis to keep the problems at bay. 

You can also install a gas leak detector to alarm you whenever a natural gas leak occurs.

Meanwhile, you can put some repellents or deterrents around the vent to disperse the small animals.

Final Thoughts

Don’t leave it unattended if you notice your ac has a smell of rotten eggs. The natural gas in your house is likely leaking, and you should leave the house immediately. 

The gas in the sewage also emits such a smell and gets into the air conditioner system, which can also put you at risk. 

To pinpoint the cause, ask the fire department, gas supplier, or plumber to fix the problem. Don’t try to deal with it yourself, especially if the problem is due to a natural gas leaking.

About The Author

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Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested dozens of products in person, like humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.

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