Is it safe to store gasoline in a garage with a water heater or furnace nearby?

Short answer

Why people ask this

People worry specifically about pilot lights, burners, and ignition sparks from a nearby water heater or furnace. They also wonder whether “sealed combustion” or electric units change the risk. Gasoline vapors are heavier than air and can travel across a garage floor toward an appliance. Codes, distances, and container types can be confusing, and attached garages add extra considerations.

When it might be safe

• You use an approved metal safety can with a flame arrester and spring-closing lid, kept tightly sealed and in good condition.
• The heater/furnace is sealed-combustion or direct-vent (no open flame or burner air intake in the garage), and the container is stored as far as practical from the appliance.
• The container is elevated or isolated so floor-level vapors can’t drift to a pilot light or burner area, and the garage is well ventilated.
• Only small quantities are stored (per local code, often a single small container), and you verify any required minimum clearance from ignition sources.
• The container is kept off the appliance platform and away from floor drains, sumps, or channels that could carry vapors to the heater.

When it is not safe

• Placing gasoline on the floor near a water heater or furnace with a pilot light, open burner, or exposed ignition source.
• Using unapproved containers (e.g., milk jugs) or old plastic cans with degraded seals that can leak vapors toward the appliance.
• Storing multiple cans or bulk fuel in an attached garage, especially in warm areas where containers can pressurize near the heater.
• Keeping gasoline near an atmospheric-draft water heater’s burner compartment, combustion air intake, or under the flue draft hood.
• Setting the can on the heater/furnace platform or within the burner service area, where normal cycling can spark or ignite vapors.

Possible risks

• Vapor ignition from a pilot light, burner spark, relay, or hot surface igniter on the water heater or furnace.
• Vapors pooling at floor level and traveling to the appliance, causing a flash fire that can spread to the structure.
• Heat from the appliance increasing container pressure, leading to leaks or venting of flammable vapors.
• Static discharge or spillage during handling that finds an ignition source in the appliance area.
• Corrosion or gasket failure on old containers allowing chronic vapor release near combustion equipment.

Safer alternatives

• Store gasoline in a detached, ventilated shed or a listed flammables cabinet away from any appliance or ignition source.
• Use a Type I/II metal safety can with flame arrester and keep it in the coolest, most ventilated, and most remote corner of a detached structure.
• Reduce quantity on hand and buy fresh fuel as needed; if you must keep some, follow local limits and add fuel stabilizer for longevity.
• If replacing equipment, consider sealed-combustion/direct-vent or electric water heaters that don’t draw combustion air from the garage.
• Create a dedicated secondary containment tray or bin that’s elevated and distant from any heater/furnace area to limit vapor travel.

Bottom line

Storing gasoline in a garage with a water heater or furnace nearby can be acceptable only if vapors can’t reach ignition sources, you use approved safety cans, maintain plenty of separation, and follow local code. When in doubt, move the fuel to a detached, ventilated location or a listed flammables cabinet.

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