Propane Leak Symptoms and the Safe Next Step

If you smell propane, hear hissing, or a propane-gas detector alarms, get everyone and pets away immediately. Do not search for the leak or operate anything that could create a spark. Once you are safely away, call 911 or the fire department and your propane supplier.

The U.S. Consumer Product Safety Commission says to leave immediately and contact local gas authorities from outside. Do not operate lights, phones or other electronics before leaving. The Propane Education & Research Council (PERC) says to stay away until an emergency responder, propane retailer or qualified professional declares the area safe (CPSC, PERC).

Signs that require action

What you notice	Safe next step
An unfamiliar gas odor	Treat it as a leak even if you are unsure of the source. Leave immediately.
Hissing near a tank, hose, regulator, heater or generator	Move away. Do not approach to inspect or shut down the equipment.
A propane-gas detector alarm	Evacuate even if you smell nothing.
Unexpectedly high propane use	It may indicate a leak. Stay clear and call the propane supplier for an inspection. If there is also odor, hissing or an alarm, evacuate and call emergency services.
Dizziness, confusion or unusual agitation near propane equipment	Get outside immediately. From a safe location, call 911, especially if symptoms continue or anyone has trouble breathing, collapses or loses consciousness.
Headache, dizziness, weakness, nausea, vomiting, chest pain or confusion near a running heater or generator	Suspect carbon monoxide (CO). Get outside immediately and call 911.
Skin or eye exposure to liquid propane	Move away from the release and obtain urgent medical help; liquid propane can cause frostbite.

PERC identifies odor, a propane-detector alarm, hissing and unusual fuel use as possible leak indicators. A leak may not be smelled because propane can collect near the ground, airflow can disperse the odor, other smells can mask it, or a person can develop odor fatigue (PERC safety guide). No odor does not establish that an area is safe.

At high concentrations, propane can displace oxygen. NIOSH lists dizziness, confusion, excitation and asphyxia as inhalation effects; contact with liquefied propane can cause frostbite (NIOSH Pocket Guide). Do not wait for symptoms before leaving: leaked propane can also ignite.

Propane leaks and carbon monoxide are different hazards

Unburned propane is the fuel escaping during a leak. Carbon monoxide is an odorless, colorless poison produced by combustion and can accumulate when generator exhaust enters a building or fuel-burning equipment is used improperly.

Symptoms cannot reliably tell you which hazard is present. A propane detector and a CO alarm also detect different gases; one does not replace the other. CDC lists headache, dizziness, weakness, nausea, vomiting, chest pain and altered mental status among the most common signs of CO poisoning (CDC). If a CO alarm sounds or people develop these symptoms near operating fuel-burning equipment, go outside and call 911.

Never operate a portable generator in a home, basement, garage, crawlspace, shed, porch or carport. CPSC specifies outdoor operation at least 20 feet from the house, with exhaust directed away from buildings and openings (CPSC). See whether a generator can be run or stored in a shed for the distinction between storage and operation.

Do not investigate or repair the leak

During a suspected leak:

• Do not switch lights or appliances on or off.
• Do not use a phone until you are safely away.
• Do not smoke, vape, light a flame or start a vehicle nearby.
• Do not unplug equipment or open an automatic garage door.
• Do not perform a soap-bubble test or search for the source.
• Do not relight an appliance, restart a generator or turn the propane supply back on.

Evacuation comes first. Only close the main tank valve if it is safely accessible and doing so does not require approaching a suspected tank leak; never delay leaving to reach it. PERC says the entire propane system must be checked for leaks by the retailer or another qualified professional before propane appliances are used again (PERC). Do not attempt a DIY repair.

If fire is present or a tank is hissing or venting, increase your distance and follow emergency responders’ instructions. For more context, see what changes the risk of a propane-tank explosion.