What does a gas leak smell like?

Natural gas is naturally odorless. Utility companies add an odorant called mercaptan, which smells distinctly like rotten eggs, sulfur, or boiled cabbage, alerting occupants to the hazard.

What should I do first if I smell a gas leak in my house?

Evacuate the property immediately. Do not switch lights on or off, do not use phones indoors, and do not start vehicles in the garage. Call 911 and your natural gas provider (Southwest Gas at 877-860-6020) from outdoors.

How do plumbers locate a gas leak after the gas company shuts off service?

Specialized gas line contractors isolate the plumbing system, attach pressure manometers to measure air decay, and run electronic combustible gas sniffer probes along all joints, unions, and valves to pinpoint the micro-breach.

Gas Leak Emergency Guide

Gas Leak Signs, Safety & Detection Testing Guide

By Leak Detection Pro Technical Team • October 3, 2026 • 6 min read

EMERGENCY WARNING: If you detect a strong odor of rotten eggs or hear high-pressure hissing near a gas meter or furnace, leave the building immediately on foot. Do not flip light switches, light matches, open garage door openers, or use indoor phones. From a safe distance outside, call 911 and Southwest Gas at (877) 860-6020.

A combustible gas leak represents an immediate life-safety emergency. Whether caused by aging black iron pipe threads, damaged flexible appliance connectors, or outdoor digging into gas risers, understanding how to recognize a gas leak and how certified technicians pinpoint hidden gas line leaks is vital for every homeowner.

Technician testing gas pipe valve unions with electronic combustible gas sniffer probe — Handheld combustible gas detectors measure parts-per-million (PPM) concentrations to isolate microscopic leaks.

How to Detect a Gas Leak: 3 Sensory Checks

Natural gas (methane) and liquefied petroleum gas (propane) provide efficient heating, cooking, and water heating, but require rigorous containment:

Smell: In its raw state, natural gas is completely colorless and odorless. Energy utilities inject a chemical compound named mercaptan, creating a pungent sulfur or rotten-egg odor that humans can detect even at parts-per-billion levels.
Sound: An active breach in a gas line often emits a persistent whistling, hissing, or roaring sound near gas furnaces, water heaters, kitchen ranges, or exterior meters.
Sight: Outdoors, look for dirt or dust blowing upward from dry ground, bubbling in standing rainwater puddles, or patches of yellowed, dying vegetation directly above buried gas service lines.

Step-by-Step Emergency Response Protocol

Evacuate Everyone Immediately: Get all household members and pets outside without delay. Leave doors open behind you to ventilate if safe to do so.
Avoid Any Ignition Source: Do not touch light switches, lamps, doorbells, ceiling fans, or appliances. Do not light a candle or cigarette. Do not turn your car engine on inside an attached garage.
Dial Emergency Services from Outdoors: Call 911 and your natural gas utility once you are at a safe distance. The utility will dispatch an emergency technician to shut down the gas meter and secure the perimeter.
Schedule Professional Gas Line Repair: Once the emergency utility response has locked the meter for safety, you must hire a licensed plumbing and gas contractor to perform isolation pressure testing, locate the failure, make repairs, and schedule a city inspection before the utility will unlock the meter.

How Technicians Pinpoint a Gas Leak

After the utility company locks the meter, gas line specialists use precision instruments to isolate the breach:

Testing Method	How It Works	Application
Digital PPM Gas Sniffer	Sensitive semiconductor probes measure parts-per-million methane and propane concentrations along joints and valves.	Pinpointing micro-leaks at appliance connections and manifolds.
Pressure Decay Manometer Test	The entire gas system is charged with 15–20 PSI of compressed air. A digital manometer tracks pressure loss over 15–30 minutes.	Confirming closed-loop gas line integrity for city inspection.
Snoop Liquid Bubble Solution	Surfactant micro-bubble solution applied to threaded fittings forms clinging bubbles at leak points under pressure.	Visual confirmation of joint failure.

Learn more about our dedicated gas leak detection services and read our overview on pipe leak repair procedures.

Need a licensed gas leak detection specialist in Phoenix?

Connect with vetted local contractors equipped with electronic sniffers and pressure testing equipment.

Call Now: (602) 836-3562

Frequently Asked Questions

Will Southwest Gas fix a leak inside my house?

No. Utility companies are responsible for lines up to the gas meter. Any piping running from the meter into your home, water heater, furnace, or outdoor kitchen is the homeowner's responsibility and must be serviced by a licensed plumbing/gas contractor.

Why does the gas utility lock my meter after an emergency?

For public safety, the utility locks the meter until a licensed plumbing contractor certifies that all leaks have been repaired and the line successfully holds an official pressure test under municipal code.

Can a slow gas leak make me sick?

Yes. Low-level chronic exposure to gas leaks can produce symptoms including headaches, dizziness, nausea, fatigue, eye irritation, and difficulty breathing. Install dual carbon monoxide and combustible gas alarms for continuous protection.