Response tactics for outdoor leaks differ from those for indoor leaks, as gas leaks from outdoor sources may involve higher-pressure pipelines.

Be alert for the distinctive, sulfur-like or rotten-egg odor of mercaptan as well as any of the following gas leak warning signs:

• A hissing, whistling, or roaring sound
• Dirt spraying or blowing into the air
• Continuous bubbling in water
• An exposed pipeline after an earthquake, a fire, a flood, or other disaster
• A damaged connection to a gas appliance
• Dead or dying vegetation (in an otherwise moist area) over or near a pipeline