Signs of a Gas Leak

The Rotten Egg Smell

Natural gas is odorless in its raw form. Gas utilities add a chemical called mercaptan (also called methanethiol) that produces a strong sulfur or rotten egg smell. This is deliberately pungent — even a small gas leak should produce a noticeable odor.

If you catch a whiff of rotten eggs or sulfur in or around your home, especially near gas appliances or pipes, treat it as a potential gas leak until proven otherwise.

Visual Signs

Gas leaks aren't always obvious, but they sometimes leave visible clues:

• Dead or dying vegetation in an otherwise healthy area, particularly along the path of an underground gas line
• Bubbles in standing water — puddles, wet soil, or flooded areas near a gas line
• White mist or fog near a gas line that doesn't match the weather
• Dirt or dust blowing from the ground when there's no wind
• Exposed piping that looks corroded — rust, pitting, or visible deterioration on gas pipes

Sounds to Listen For

A gas leak can sometimes be heard before it's smelled:

• Hissing or whistling near a gas line, meter, or appliance connection
• Roaring or blowing sounds from a larger leak in a distribution line
• Unusual sounds from gas appliances — popping, banging, or irregular flame patterns

Physical Symptoms

Prolonged exposure to natural gas can cause health effects. If multiple people in a building experience these symptoms simultaneously, a gas leak may be the cause:

• Headaches and dizziness
• Nausea and fatigue
• Difficulty breathing or shortness of breath
• Lightheadedness or feeling faint
• Eye, nose, or throat irritation

These symptoms may be mild at first and worsen with continued exposure. If you feel better after leaving the building and worse when you return, that's a significant warning sign.

Gas Leak vs. Other Smells

Not every sulfur-like smell is a gas leak. Here's how to tell the difference:

• Sewer gas smells similar but usually comes from drains, especially if they've dried out. Running water in unused drains often resolves it.
• Skunk spray can be confused with mercaptan, but it's typically strongest outdoors and fades over time.
• Electrical burning has an acrid, plastic quality that's distinct from the rotten egg odor of natural gas.

When in doubt, treat it as a gas leak. The consequences of ignoring a real leak far outweigh the inconvenience of a false alarm.