Leak Detection Guide
Natural gas and propane are naturally odorless, which would make leaks nearly impossible to detect by smell. Utilities solve this by adding mercaptan, a sulfur-based compound, in tiny concentrations — enough that even a small leak produces a smell most people notice immediately.
Leave the building right away without stopping to investigate the source. Once you're a safe distance away, call your gas utility's emergency line or 911 — both are equipped to respond to gas leak reports quickly, and neither will fault you for a false alarm.
A hissing sound near a gas line, meter, or appliance connection is a strong secondary sign. Outdoors, a patch of dead or discolored grass with no other explanation can indicate an underground gas line leak, since escaping gas displaces oxygen in the soil around plant roots. A gas bill that's climbed with no change in usage is a slower-moving sign worth checking too.
Don't flip any light switches, don't use your phone inside the building, don't light a match or use any open flame, and don't try to locate the leak yourself. Any spark, however small, can ignite accumulated gas — this is the one leak type where confirming it yourself is never worth the risk.
Both use similar mercaptan-based additives and smell broadly similar — a sulfur or rotten-egg odor. Propane, being heavier than air, tends to pool low to the ground rather than dispersing upward, which is why propane leaks are often noticed first near floor level or outdoor tank areas.
For an active, currently-smellable leak, always call the utility or emergency services first — they can shut off gas at the meter, which a private inspection can't do. Once the immediate danger is addressed, a leak detection service locates the exact point of failure so it can actually be repaired, since the utility's emergency response doesn't include finding or fixing the leak itself.
