Propane Safety for Grills and Patio Heaters: Tanks, Leaks and CO

Propane holds about 21,548 BTU per pound. Divide the stored BTU by the appliance's BTU per hour to get hours at full output; at half throttle, double it. A full 20 lb tank holds about 431,000 BTU. The table uses that math for three typical loads.

An overfilling prevention device (OPD) is a float-operated shutoff inside the tank valve that stops filling when the tank reaches about 80 percent of its liquid capacity. NFPA 58 requires OPDs on the portable cylinders used for grills and heaters, from 4 lb through 40 lb capacity. You can recognize an OPD valve by its triangular handwheel. A filling station should refuse an older cylinder with a round or star-shaped handwheel.

The 20 percent headspace exists because liquid propane expands significantly as it warms. A tank filled to the brim on a cool morning and left in the sun can build pressure until the relief valve vents gas, which is dangerous near any flame. That is why a properly filled "20 lb" tank holds about 20 lb of propane in a cylinder that could hold more, and why you should never try to overfill one.

• Tare weight: the empty weight, stamped on the collar as "TW". A standard 20 lb grill cylinder commonly has a tare weight around 17 lb, so it weighs roughly 37 lb when full. Subtract tare from a scale reading to see how much propane remains; a Flame King digital tank scale does this quickly.
• Date stamp: the collar also shows the manufacture date. DOT cylinders generally must be requalified 12 years after manufacture before they can be refilled, and refill stations check.
• Condition: do not fill or use tanks with deep dents, bulges, heavy rust or a damaged collar or foot ring.

Refilling usually gives you more propane for the money, because many exchange programs fill 20 lb cylinders with about 15 lb of propane. You pay only for what goes in, and you keep a tank whose history you know. Exchange is faster, available at more stores and lets you hand off an out-of-date or worn cylinder without paying for requalification.

Either way, inspect the tank you walk away with: an OPD triangular handwheel, a legible date within the requalification period, no significant rust or dents, and a valve that is fully closed with its cap or plug in place. Keeping a second full tank, such as the Flame King YSN230 20 lb tank with gauge, ends mid-cook runs to the store. A Flame King Bluetooth tank scale reports the level to your phone.

Transport tanks as briefly as possible, upright, secured and ventilated, following CPSC and propane industry guidance:

• Close the valve fully and keep the valve plug or cap in place.
• Stand the tank upright and secure it so it cannot tip or roll, using a crate, a propane tank stabilizer or a seat belt on a floor-standing tank.
• Put it in the passenger area or an open truck bed with windows cracked, not in a closed trunk.
• Drive directly home. Never leave a tank in a parked car, especially in heat, where pressure rises and the relief valve can vent into the cabin.
• Do not smoke in the vehicle and do not carry more tanks than you need; many states and local codes limit how many cylinders can be carried in a passenger vehicle.

Outdoors, upright, in a ventilated spot away from the house's openings. NFPA 58 and CPSC guidance both say not to store portable propane cylinders indoors. That includes garages, basements, sheds attached to the house, enclosed porches and cars. A leak indoors pools at floor level where water heaters, furnaces, dryers and light switches can ignite it.

• Keep tanks off damp ground if possible to limit foot ring rust, and out of direct afternoon sun.
• Keep spare tanks away from the grill or heater they are not connected to, and away from dryer vents, air conditioner condensers and window wells.
• Store the tank on the grill connected only if the valve is closed; many manuals recommend disconnecting for long storage.
• When you move a grill into a garage or shed for winter, disconnect the tank first and leave the tank outside.
• Store 1 lb cylinders outdoors too, with caps on, and do not refill disposable cylinders.

The regulator drops tank pressure to the low pressure the appliance needs. Treat it as a wear part:

• Inspect each season for cracks, abrasion, brittleness, kinks and melted spots on the hose, and for corrosion or damage on the regulator vent. Replace, do not tape.
• Low flame after connecting usually means the regulator's excess flow device tripped because the tank valve was opened fast or a burner was on. Turn all burners off, close the tank valve, disconnect, wait a minute, reconnect and open the tank valve slowly.
• Use the right parts. Use only the regulator and hose specified for your appliance. Adapter hoses that let 1 lb cylinder appliances run from a 20 lb tank, such as the Gas One 4 ft adapter hose or the Blackstone 5471 hose and regulator for Blackstone tabletop griddles, should match the appliance maker's guidance and be leak tested like any other connection.
• Keep the regulator vent pointing down or covered as the manual shows, so rain and insects cannot block it.

Use the clearances printed in your appliance manual and on its rating plate; they vary by model and there is no universal number. Grill manuals commonly specify clearances from combustible construction at the sides and back and warn against use under unprotected combustible overhangs. Patio heater manuals list overhead clearance to ceilings, awnings, umbrellas and tree branches plus side clearance to walls, because a mushroom heater sends much of its heat upward and outward.

• Keep grills and heaters off wood decks under low eaves and away from vinyl siding, which can warp.
• Never place a patio heater under a patio umbrella or fabric awning.
• Many fire codes restrict gas grills on combustible balconies of apartments and condominiums; check with your building and local fire marshal.
• Set heaters on a level, hard surface and use their tip-over protection: the Fire Sense 61130 and Amazon Basics 46,000 BTU heater list tilt shutoffs, and the Hiland HLDS032 tabletop heater lists thermocouple and anti-tilt shutoffs.
• Do not run a heater in strong wind; blowouts and tip-overs are both more likely. If a flame goes out, turn it off and wait before relighting.

No. Outdoor propane grills, griddles and patio heaters are designed and certified for use outdoors with open air on all sides. Burning propane consumes oxygen and produces carbon monoxide, an odorless gas that can kill in minutes in an enclosed space. An open garage door or a screened porch does not make it safe, and neither does "only for a few minutes". CPSC warns specifically against using grills and outdoor heaters indoors, in garages, tents or other enclosed areas.

Carbon monoxide poisoning symptoms include headache, dizziness, weakness, nausea, confusion and sleepiness. If anyone feels these near a fuel-burning appliance, get everyone into fresh air and call 911. Install CO alarms inside the home on every level and near sleeping areas, and test them regularly. If you want heat under a covered or partly enclosed patio, choose an electric infrared heater installed to its manual, such as the Bromic Tungsten 4000W or Dr. Infrared DR-239; see best electric patio heaters and electric vs propane patio heater.

A rotten-egg smell means propane is escaping. Act in this order:

1. If the grill is not lit: do not light it or use any flame. Turn off the tank valve and all burner knobs if you can reach them safely.
2. If the grill is lit: turn off the tank valve and burners only if you can do so safely. Close nothing that traps gas; keep the lid open.
3. Move away from the grill and keep children, pets and others back.
4. If the smell continues after the valve is closed, or you cannot reach the valve, call the fire department from a safe distance.
5. If the smell is inside the house, leave immediately without operating light switches, phones or appliances inside, and call 911 or your gas supplier from outside.
6. Before using the grill again, perform a soapy water leak test and replace any leaking part. If a fire starts at the tank or regulator, get away and call 911; do not try to move the tank.