How should I store a gas bottle in hot weather?

Pressure in an LPG cylinder rises with temperature, so summer storage is about shade, ventilation and keeping it upright and outdoors — not about how much is left in it.

Difficulty: beginner
Time: 12 min
Read: 5 min
Safety: warning

Short answer

Store cylinders outside, upright, in shade, on firm level ground, with the valve closed. Never below ground level, never in a sealed shed or a car, and never indoors. Cylinders have a pressure relief device that vents if they overheat — which is a safety feature working, and a serious hazard if it happens somewhere enclosed.

Barbecue season is when most people handle an LPG cylinder, and it is also when the storage matters most, because the propellant inside is a liquid in equilibrium with its vapour and the vapour pressure rises steeply with temperature. None of this is a reason to be frightened of a gas bottle. It is a reason to keep it in the one place that is genuinely correct, which happens to be the easiest place anyway.

Safety

LPG cylinders must be stored and used upright, outdoors, in a ventilated place out of direct sun, and never in a cellar, under a floor, in a drain area or anywhere below ground — LPG is heavier than air and collects in low spaces where it can reach an explosive concentration. Never store a cylinder indoors, in a car boot, or in a sealed shed. If you smell gas, do not operate any switch: turn the valve off if it is safe to reach, ventilate, get everyone out and call the emergency gas number.

Step by step

Keep it outdoors, always.LPG cylinders belong outside, including when empty and including over winter. An empty cylinder still contains vapour. Indoors is not a location that becomes acceptable if the bottle is small, nearly empty or only there overnight.
Keep it upright.Cylinders are designed to draw vapour from above the liquid. On its side, liquid can reach the valve and the regulator, which is not what either is designed for and can produce a flame far larger than expected. Upright in storage, upright in transport, upright in use.
Keep it out of direct sun.Direct sun raises the cylinder's temperature and therefore its internal pressure. Shade from a wall, a purpose-made cylinder cover or a ventilated store is enough. What matters is shade with air movement, not an enclosure.
Never store below ground level.LPG vapour is heavier than air, so a leak in a cellar, an inspection pit, a sunken patio or near a gully collects rather than dispersing. That is how a small leak becomes an explosive atmosphere. Above ground, in the open air, is the rule.
Do not seal it into a shed or a cupboard.A sealed store defeats the point. If a cylinder is kept in a structure it must be well ventilated at both high and low level, and it must not be a space where people or ignition sources are. A hot sealed shed is the worst of both — high temperature and no dispersal.
Close the valve when it is not in use.Every time, not just at the end of the season. The valve, not the appliance control, is what makes a cylinder safe when you walk away from it.
Transport it properly and get it out of the car immediately.Upright, secured so it cannot roll, valve closed, with a window open, and never left in a parked car. A cylinder in a hot boot is precisely the combination of enclosure, heat and no ventilation to avoid. Take it straight from the shop to its outdoor storage place.
Check the hose and regulator at the start of the season.Rubber hose perishes, cracks and hardens, particularly where it has been in sunlight. Check for cracks, check the date if it carries one, and test connections with soapy water — bubbles show a leak. Never test with a flame.
Know what the relief valve does.Cylinders have a pressure relief device that releases gas if internal pressure rises too far, for example in a fire or extreme heat. It exists so the cylinder does not rupture. It also means an overheating cylinder can release flammable gas, which is survivable outdoors in the open and extremely dangerous in an enclosed space.

Tips

A simple cylinder cover or a shaded corner of the garden is all the storage most people need. Elaborate enclosures usually make ventilation worse, not better.
Keep the cylinder away from airbricks, drains and gully gratings, since these are the routes by which a leak reaches an enclosed space under a building.
Change cylinders outdoors, with no ignition source nearby and nobody smoking, and check the connection with soapy water afterwards.
Do not paint a cylinder, remove its markings or attempt to repair a valve. Cylinders are the supplier's property and their condition is their responsibility — exchange a damaged one.
Store spare and empty cylinders in the same conditions as full ones. An empty cylinder still holds vapour and is still a pressure vessel.

Common mistakes

Storing a cylinder in the garage or a garden shed for tidiness — Enclosed storage prevents a leak dispersing and lets temperature build. Cylinders belong outside, and an attached garage is effectively part of the house.
Leaving a cylinder in the car after collecting it — A hot sealed boot is the worst combination of heat and no ventilation, and a leak in a car interior is extremely dangerous. Take it straight out on arrival.
Laying a cylinder on its side to fit it in somewhere — It allows liquid to reach the valve and regulator, which can produce a dangerously large flame at the appliance.
Testing a suspected leak with a lighter — It is exactly how people are injured. Soapy water on the joint shows a leak as bubbles, safely.

Checklist

Outdoors, above ground, never in a cellar or pit
Upright and stable on firm level ground
Shaded from direct sun, with air movement around it
Valve closed whenever it is not in use
Away from drains, gullies and airbricks
Away from ignition sources and anything flammable
Hose and regulator checked at the start of the season

Questions people ask

Can a gas bottle explode in the sun?

A cylinder standing in normal British sunshine is not going to burst — they are built with a substantial margin and fitted with a pressure relief device that vents before rupture. The real risks are a cylinder in a fire, and a leak collecting in an enclosed or below-ground space. Shade and open-air storage remove both concerns cheaply.

Where can I keep a cylinder if I only have a small yard?

Outdoors, upright, shaded, on firm ground, away from drains and airbricks and away from the door. A ventilated cylinder cover is fine. What you must not do is bring it inside or into a sealed store because the yard is small.

How much LPG am I allowed to keep at home?

There are limits on domestic quantities and they depend on the cylinder type and where they are kept, and the rules are enforced locally. Your supplier and your local fire and rescue service publish current guidance — check there rather than relying on a figure quoted second-hand, since the limits and the guidance change.