Why Does My Car Smell Like Rotten Eggs? (5 Reasons!)

Cleaning your car is part of the daily routine. It can be inevitable for your space to smell bad, but some foul odors may raise a concern. These odors could present the current condition of your vehicle, suggesting immediate action.

One car smell that you must be aware of is the rotten egg smell. It might sound ridiculous and not that concerning but better believe it could be something else! 

Hopefully, the question, “why does my car smell like rotten eggs?” never happens to you. But, if you need a heads up, we got you! Keep reading to understand the reason behind the rotten egg smell in your car!

The Smelly Truth Behind Rotten Egg Odor in Cars

A rotten egg smell could suggest that you may lack the proper vehicle maintenance or have been ignoring any signs of malfunctions. Its impact on one’s health depends on exposure to the substance. The effects differ for anyone from mild to severe conditions, even causing death, as H2S is a known chemical asphyxiant. Exposure to the gas is suggestive of health monitoring and treatment.

Here are following information to understand the occurrence of this specific odor better:

The Science behind the Rotten Egg Smell

A sulfur-like smell is usually a characteristic of a rotten egg odor. Hydrogen sulfide or H2S is a colorless gas naturally found in sewers, well water, and oil and gas wells. According to NIH, H2S results from the breakdown of organic materials by bacteria such as Escherichia coli without oxygen. 

H2S also occurs from human-made activities such as mining, tanning, and food processing. According to the CDC, its pungent smell is observable, especially at low concentrations ranging from 0.0005 to 0.3 ppm, as it is denser than air.  

Hydrogen sulfide gas disintegrates in the atmosphere in 3 days. However, hydrogen sulfide stays in the air for at least 1-42 days, depending on the environment and season. This gas, especially in enclosed spaces, is hazardous as it is highly toxic and extremely flammable.

A rotten egg smell usually indicates a problem and usually a propane leak. Besides your rotten egg for breakfast, there isn’t a good thing about it.

However, some incidents give a nasty smell. Rotten egg smell can come from electrical equipment, drains, mold and must accumulation, and decaying animals. These examples still require the same urgency for solutions.

Health Influences of Rotten Egg Smell

The factors of exposure to rotten egg smell determine its health effects on humans. It includes the amount, length, and route of exposure to hydrogen sulfide for a specific reaction to occur. The affected people acquire the toxic effects through inhalation or skin or eye contact.

The lowest odor threshold of hydrogen sulfide for symptoms to manifest is 0.0001 ppm, while the highest is 0.13 ppm. According to the Government of Western Australia, the dose exposure limit of 0.1 H2S grade has an average timeframe of 1 day. While a 0.014 has an average of 90 days for the effects to happen. 

The symptoms of the presented range vary from person to person. However, some possible manifestations are headache, nausea, fatigue, eye and nose irritation, and breathing difficulty.

The dangers of hydrogen sulfide happen at grade levels of 2 ppm and above. For example, a two-ppm air level with an average timeframe of 30 minutes can cause bronchial restriction. Similarly, four ppm air level causes increased eye complaints, while a 5-10 ppm can cause minor metabolic effects.

A ≥100 ppm or those with more than 1 million times greater than the amount of maximum environmental concentration are highly dangerous. This hydrogen sulfide level found from natural sources is 0.00033, presenting certain conditions. The effects include neurological and respiratory damage, and repeated exposure may cause convulsions, coronary disease, and even death.

Other factors to consider in the severity of the effects of hydrogen sulfide exposure include age, sex, diet, family traits, and lifestyle. Practice stricter monitoring of your surroundings at your house or vehicle to prevent future problems and irreversible health consequences.

Why Does My Car Smell Like Rotten Eggs?

Besides the harmful effects of rotten egg odor, no one could ever enjoy their ride experience with that smell. It could also mean your vehicle’s experiencing problems and that you should not ignore them. If you are also asking about How to Get Smoke Smell Out of Car, or how to eliminate burning rubber smell from car you can read more on our blog.

The best way to eliminate the odor is to find the root problem. Rotten egg smell in your car may be caused by damaged catalytic converter, defective fuel pressure sensor, oil transmission fuel, dirty fuel filter and many other reasons. Here are the common sources causing the rotten egg smell in your car:

Cause 1: Damaged Catalytic Converter

A common reason for the smell is a faulty catalytic converter. However, as a component of the emission system, it neutralizes emissions to produce a harmless and odorless gas. An example is converting hydrogen sulfide into a tolerable gas such as sulfur dioxide.

However, a broken catalytic converter, such as an incident with a clogged converter, will cause a disturbance in the car’s normal function. This build-up of fuel byproducts can overheat and may lead to a car fire. In addition, a vehicle unable to convert hydrogen sulfide gas causes a rotten egg smell.

Cause 2: Defective Fuel Pressure Sensor

The fuel pressure sensor manages the flow of fuel that goes through the engine. If there is a malfunction, the sensor fails to control the flow and can cause clogging of excess oil, damaging the emissions system. This problem affects the catalytic converter’s normal function, producing a rotten egg smell.

Cause 3: Old Transmission Fuel

A transmission fuel or fluid lubricates your car’s gear and emission systems. An overused or old vehicle causes worn-out seals leading to unavoidable situations such as fluid leakage into sensitive car areas. Additionally, an observable rotten egg smell happens once the leak stagnates. 

Cause 4: Dirty Fuel Filter

A fuel filter helps screen the fuel’s dirt, debris, and rust particles. In addition, this filter will help protect the engine’s significant parts, including the emission system. 

A dirty fuel filter is suggestive of accumulated contaminants. This phenomenon will lead to the burning of the converter, similarly, producing the rotten egg smell.

Cause 5: Other Possible Reasons

Other situations to consider are dead animals, hidden food residuals, or groceries. Apart from mechanical issues, the mentioned scenarios are possible. For example, rotten foods can smell like rotten eggs, and it’s better to check your car to prevent this from happening! 

Prevent This Problem from Happening Again

The best way for any unlikeable circumstances to happen is through prevention and taking matters quickly. For most engine problems, replacing or repairing these essential parts is advisable. 

According to Casey, D., replace transmission fluid with an interval of at least 12 months. A helpful way to remind you to change the transmission fluid is by checking if there is any discoloration. Then drain and replace a black or dark brown liquid that usually contains contaminants.

Besides your vehicle care, it is also essential to opt for vehicle service together with part replacements at least periodically. As much as possible, do not wait until you have worn out your engine; observe the signs that your car gives. Examples such as rattling noises, broken engine lights, and ‘the’ rotten egg smell will give you an idea of the current condition of your vehicle.

If you notice a rotten egg smell, as per OSHA requirement, to evaluate exposure, especially in confined spaces such as cars, ventilate the area. Use a car oil diffuser for a quick fix to such a smell.

There are plenty of options, and it's not always clear which one will work best. Check out our guide on how to make car freshies, for more options.

If the odor persists, often invest in other natural and chemical solutions such as vinegar and lukewarm. Nevertheless, you should remove the rotten egg as this is harmful to your health. Using different fragrance oil or car freshies may not only remove rotten smell but can also get rid of weed smell in your car.

Find That Source and Fix It!

Reduce your exposure to hydrogen sulfide by regularly cleaning and monitoring your car. Be attentive to the signs of malfunction; even a mere smell is a life changer! As they say, prevention is the best medicine, and understanding its urgency gives you an edge. If everything is already fixed and the smell still lingers, you may want to add car freshies or spray a fragrance oil like Egyptian musk oil.

So, the next time the question “why does my car smell like rotten eggs?” pop up, you know what to do! Follow our page to keep you posted!