Yes, breathing sewer gas can make you sick, and the effects range from mild to serious depending on how much you breathe and for how long

Sewer gas contains hydrogen sulfide, methane, ammonia, and carbon dioxide — all of which irritate your lungs and airways when inhaled. At low levels, you notice the smell and feel discomfort. At higher concentrations or with longer exposure, you can develop headaches, nausea, dizziness, and respiratory problems. In rare cases — usually in enclosed spaces like basements or crawl spaces where gas accumulates — sewer gas can cause loss of consciousness or death.

The risk depends on three things: how much gas is present, how long you breathe it, and whether you have existing lung problems. A brief whiff from a backed-up drain causes temporary irritation. Hours in a space with active sewer gas leakage can cause real harm. People with asthma, emphysema, or other chronic lung disease are at higher risk of serious symptoms.

Key Takeaways

  • Hydrogen sulfide in sewer gas irritates your respiratory system at any concentration, but symptoms worsen with longer exposure and higher levels.
  • Mild exposure causes headache, nausea, and eye irritation; moderate exposure can trigger coughing, shortness of breath, and dizziness.
  • People with asthma or chronic lung disease face greater risk of severe reactions, including airway constriction and difficulty breathing.
  • Enclosed spaces like basements and crawl spaces allow sewer gas to build up to dangerous levels much faster than open areas.
  • Symptoms usually fade within hours of leaving the contaminated space, but persistent exposure or high concentrations require medical attention.

Symptoms you may experience from sewer gas exposure

Short-term exposure — a few minutes to an hour — typically produces irritation symptoms. Your eyes, nose, and throat feel raw. You develop a headache. You may feel slightly nauseous or dizzy. Coughing is common because the gas irritates your airways. Most people recover completely once they leave the area and breathe fresh air.

Longer exposure or higher concentrations bring stronger symptoms. Shortness of breath becomes noticeable. Some people report a tight feeling in the chest. Nausea can progress to vomiting. Dizziness may worsen to the point where balance becomes difficult. If you have asthma, you may experience an asthma attack triggered by the irritation.

In rare cases — usually in poorly ventilated spaces where gas has accumulated for hours — people lose consciousness. This happens because hydrogen sulfide at very high levels can paralyze the olfactory nerve (the one that detects smell), so you stop noticing the gas even as you breathe dangerous amounts. This is why sewer workers and people entering confined spaces use gas detectors and breathing equipment.

Why hydrogen sulfide is the main concern

Hydrogen sulfide is the component of sewer gas that causes the most damage to your health. It is heavier than air, so it sinks and collects in low spots — basements, crawl spaces, and the lowest points of plumbing systems. Even at low concentrations, it irritates mucous membranes in your eyes, nose, and lungs.

The gas also interferes with your body's ability to use oxygen at the cellular level. At very high concentrations — which occur mainly in industrial settings or completely enclosed spaces — this can cause rapid loss of consciousness and death. However, the smell of hydrogen sulfide is so strong that most people leave the area long before reaching those levels. The exception is when the olfactory nerve becomes paralyzed by prolonged exposure, which prevents you from smelling the danger.

Who faces the highest risk from sewer gas

People with asthma, chronic obstructive pulmonary disease (COPD), emphysema, or other chronic lung conditions are more vulnerable to sewer gas. Their airways are already inflamed or narrowed, so irritation from the gas can trigger a serious reaction. A person without lung disease might cough and feel uncomfortable; a person with asthma might experience an attack that requires a rescue inhaler or emergency care.

Older adults and very young children also face higher risk because their respiratory systems are less robust. Pregnant people may experience symptoms more intensely because pregnancy changes how the lungs function. People who work in sewers, septic tank maintenance, or plumbing are at occupational risk and should use proper ventilation and protective equipment.

Enclosed spaces where sewer gas builds up fastest

Basements are the most common problem area in homes. If your sewer line has a crack or your plumbing is not properly vented, gas can seep into the basement where it accumulates because there is no air circulation to disperse it. Crawl spaces under houses have the same problem. Bathrooms with poor ventilation can trap gas if the vent stack is blocked or damaged.

Septic tank areas and the ground directly above a failing septic system can release sewer gas into the air above. Laundry rooms with floor drains that dry out lose their water seal, allowing gas to rise from the drain. Any space where plumbing drains are present but not regularly used — a guest bathroom, a basement sink, a floor drain in a garage — can become a source of gas if the water trap dries out.

What to do if you think you have been exposed

Leave the area when ready and go outside or to a well-ventilated space. Open windows and doors to let fresh air in. Most symptoms fade within 15 to 30 minutes once you are breathing clean air. If symptoms persist after an hour, or if you experience chest pain, severe shortness of breath, or confusion, seek medical attention.

Tell the doctor or emergency room staff that you were exposed to sewer gas. This helps them understand what they are treating. There is no specific antidote to sewer gas exposure — treatment focuses on supporting your breathing and managing symptoms while your body recovers. Oxygen may be given if your oxygen levels are low.

After you recover, identify the source of the gas. Check for backed-up drains, cracks in sewer lines, dried-out water traps, or blocked vent stacks. A plumber can inspect your system and repair the problem. Do not ignore repeated exposure — it suggests an ongoing leak that needs professional attention.

How to reduce your risk at home

Keep water seals intact in all drains. If you have a floor drain, sink, or toilet that is not used regularly, run water through it weekly to maintain the water trap that blocks gas from rising. Make sure your plumbing vent stack is clear and extends above your roof — a blocked vent forces gas to back up into the house.

may support your basement and crawl space have adequate ventilation. Cracks in your foundation or sewer line should be repaired by a professional. If you smell sewer gas in your home, do not assume it is harmless — have a plumber inspect the system. Proper ventilation fans in bathrooms and kitchens also help prevent gas buildup.

Frequently Asked Questions

Can sewer gas cause permanent lung damage?

Single or brief exposures do not cause permanent damage. Repeated or prolonged exposure over weeks or months might contribute to chronic respiratory problems, but this is rare in residential settings. If you work in sewers or septic maintenance and have repeated exposure, talk to your doctor about lung function testing.

Is the smell of sewer gas a sign it is dangerous?

The smell is a warning, but it is not a reliable measure of danger. At very high concentrations, hydrogen sulfide can paralyze your sense of smell, so you stop detecting it even as you breathe unsafe amounts. This is why sewer workers use gas detectors rather than relying on smell alone.

What if I have asthma and live in a house with sewer gas problems?

Have the plumbing inspected and repaired as soon as possible. Sewer gas can trigger asthma attacks, and repeated exposure increases the risk. In the meantime, keep your rescue inhaler with you, may support good ventilation in your home, and consider using an air purifier with activated carbon in rooms where you spend the most time.

How long does it take to recover from sewer gas exposure?

Most people feel better within 30 minutes to a few hours of leaving the contaminated space. Mild symptoms like headache or nausea usually resolve completely. If symptoms last longer than a few hours or worsen, seek medical attention to rule out other problems.

Can sewer gas seep into my home from the street?

Yes, if your sewer line has a crack or break, gas can seep into the soil around your foundation and enter through cracks or gaps. If you smell sewer gas outside near your house or in your basement, have a plumber inspect your sewer line. They can use a camera to check for breaks and recommend repairs.