Can you leave a gas canister attached to a camping stove?

During a meal, yes: the canister stays on while you cook, including the pause between one pot and the next. Once the meal is over and the stove has cooled, unscrew it, as MSR, Jetboil and Primus all say to do after use and before storing. MSR's support team goes further and says to unscrew it even between breakfast, lunch and dinner, because the joint is not leak proof.

What "attached" means: one valve, two seals#

A screw-on gas canister is a small steel can of liquid gas under pressure, with a threaded valve on top built to the European standard EN 417. That valve is called a Lindal valve, after its maker, and the part itself is the Lindal B188.

A small stem sits in the middle of the can's top, and a rubber seal grips it to hold the gas in. One cartridge maker describes a seal "usually EPDM or NBR" (two kinds of synthetic rubber) that "presses tight around the stem". When you screw a stove on, its fitting presses the stem in and opens the gas path. When you unscrew, the stem rises and the seal closes again.

So a canister on its own has one seal, the valve in its top. Screw a stove on and that seal is held open on purpose, and the gas is now kept in by two other parts:

• The O-ring in the stove's base. An O-ring is a small rubber ring that presses against the top of the can as you tighten the stove, sealing the joint between can and stove.
• The stove's own control valve, the knob you turn to light and shut off the flame.

Turning the knob off stops gas reaching the burner, but it does not close the canister. The gas is still in the stove body, held back only by the O-ring and the knob's valve. Which? makes the point in plain words: while the cartridge is screwed in, "there's a route for the gas to get out of the canister."

That second route is the whole question. A canister alone has one seal, built for storage, while a canister with a stove on it has a held-open valve, a rubber ring under pressure and a knob. More parts means more places to leak.

What the stove manuals say#

Every source read for this page says the same thing, and they differ only in how far they take it.

No manual read here says it is fine to leave the stove on the can between meals, and none says it is fine to pack them joined. The only gap they leave open is the one inside a meal, and the manuals answer that by their order of steps: connect, cook, turn off, cool, unscrew. A second pot of water before you turn off and cool is part of the same use.

Why forum answers disagree#

Search this question and most of what comes back is forum threads. Some people leave the stove on the can all trip and say nothing has ever gone wrong, while others unscrew every time. Both camps are partly right, and the Cascade article shows where each goes wrong.

"The knob is off, so nothing can leak." This is the common belief, and it is the one the manuals reject. The knob is not the canister's seal. The O-ring is in the gas path now, and Cascade says plainly that the joint "is not completely leak proof", just like the joint between a home barbecue and its propane tank.

"It leaks, so it is dangerous." This overstates it for a stove that is in good order. In Cascade's own words the slow leak between meals is "not enough to cause harm", and what it does cost is fuel: "enough that you may run low on fuel if you leave the two mated overnight."

For a sound stove on a clean can, then, leaving it on between meals is mostly a fuel cost. The danger grows with three things: a worn or dirty O-ring, cold that stiffens the rubber, and a closed space where gas can build up. Storage and packing add a fourth, which is force on the threads. That is why every maker draws the line at storage, and why MSR's support team draws it earlier still.

How much gas does unscrewing waste?#

The best argument for leaving the canister on is the hiss you hear when you unscrew it, which sounds like waste. Cascade calls it normal: "A small amount of fuel pressure escaping when attaching and detaching is normal though and to be expected." The MSR manual says the same: "A small amount of gas may escape when unscrewing stove."

No maker publishes how small, but a few simple sums put the hiss in proportion.

A gram of isobutane, the main gas in most canisters, is 0.41 litres of gas at room temperature and normal air pressure. That comes from its molecular weight (58.1 grams per mole, NIST) divided into the volume a mole of any gas takes up at 20 degrees C (24.06 litres), and the same sum gives 0.55 litres per gram for propane. So losing one gram means letting out 0.4 to 0.55 litres of gas, about the volume of a large drinks bottle.

Now put that gram into cooking. The stove fuel planning guide uses 18 g of gas for each litre of water boiled with a lid and a windscreen, so one gram boils about 55 mL of water, a few sips of tea. You do not need to guess your own figure, because a kitchen scale settles it.

The canister weighing guide has the empty can weights you need to turn the same scale reading into gas left. The point of the test is the comparison: the unscrewing loss is a small amount you can measure, while the slow leak from leaving them joined has no published rate and depends on the state of one rubber ring.

A worked case: three days, nine meals#

Take a three-day trip with a canister stove and one 230 g canister, and suppose you cook three times a day, so nine meals. Walk through both habits.

Habit one: leave it on for the trip. You screw the stove on once at the trailhead, turn the knob off after each meal and leave it. Between meals and overnight the joint is under pressure for around 60 hours. Cascade says a stove in this state "can leak very slowly", with no rate given. On a cold night the O-rings stiffen, which both MSR and Jetboil warn can cause a leak. Each morning the stove goes into your pack still on the can, with its weight bearing on the valve threads.

Habit two: unscrew after each meal. That is nine connections and nine unscrewings. Suppose each one hisses away a full gram, which would be a long hiss of 0.4 litres; then the trip costs 9 g, or half a litre of boiled water over three days at 18 g per litre. If your hiss is shorter the cost is smaller, and the weighing test above will tell you by how much.

Worked through, the choice is between a cost you can weigh and a leak that depends on the rubber. Habit two also keeps the stove off the valve threads in your pack, which is the case every manual makes.

The rule, situation by situation#

Packing and storing the stove#

Packing is where the manuals are firmest, and three things from the sources explain why.

First, the stove holds the canister's valve open, so in a pack the only seals left are the O-ring and the knob.

Second, the threads take the load, because the stove is a lever on top of the can. The Wikipedia page on EN 417 notes that the valve's "thread can be damaged by external force". MSR warns that even over-tightening "can damage stove or canister and cause fuel to leak". A stove knocked sideways in a pack is that kind of force, applied through a lever.

Third, the canister's own seal is the one built for storage, and unscrewed, the can is back to one closed valve. Jetboil adds a last step: refit the plastic cap over it.

For home storage, MSR's manual gives the limits: somewhere well ventilated, away from heaters and pilot lights, and never above 120 degrees F (49 degrees C). Cascade's storage article adds cool, dry and upright. A car in summer can pass that limit; leaving canisters in a hot car has the cabin temperatures. The wider routine is in storing gear between trips.

One correction to a common claim. The MSR manual's minus 18 degrees C (0 degrees F) limit is for the stove, which it says should not be used or stored below that; it is not a canister storage rule. And Cascade's storage article tells you to keep canisters inside your pack or sleeping bag in the cold, not in use, to keep their pressure up. What must never happen in a tent is lighting the stove, because of carbon monoxide.

Cold weather makes the joint weaker#

Two makers give the same warning in nearly the same words. MSR: "In freezing temperatures O-rings can stiffen and leak fuel." Jetboil: "In temperatures below freezing, O-Rings may not seal fully, resulting in a fuel leak."

That matters here because the O-ring is the part a joined stove and can depend on, so a stove left on a can through a frosty night has its weakest seal at its coldest. MSR's answer is to "check for fuel leaks before and after lighting". In practice, unscrew the stove at night, keep the can warm as Cascade suggests, and screw it on again in the morning.

The pressure side of cold canisters is a separate problem, covered in canister stoves in the cold.

How to check the joint for a leak#

You can run this at home with washing-up liquid and water, following the soapy water method that MSR's manual and Which? both give.

1. Check the O-ring first. Look in the stove's base; MSR says not to use a stove with "damaged or worn seals".
2. Clean both sides. Cascade suggests an old toothbrush on the stove's connection and the canister valve, since even a grain of sand can stop the seal.
3. Screw on straight, by hand. Keep the stove upright over the can, because Cascade warns that screwing on at an angle can cross-thread it, and do not over-tighten.
4. Brush soapy water on the joint with the knob shut. Growing bubbles mean a leak, and you should never test with a flame.
5. If it leaks, unscrew it. Cascade's rule: if the leak stops once the stove is off, the stove's gasket is the likely fault, so stop using the stove. If gas keeps coming from the canister, its valve has failed: leave the can outdoors until it stops, and do not use it again.

Common mistakes#

Trusting the knob. Turning the flame off does not close the canister, and the gas still sits in the stove body behind the O-ring.

Packing the stove on the can. The valve is held open and the threads take every knock, which is why every manual read here says unscrew first.

Unscrewing a hot stove. MSR says wait 5 minutes after the flame goes out, and Jetboil and Primus both say check the burner is out before you disconnect.

Reading a hiss as a fault. A short puff as the threads engage or release is normal, Cascade says, but a hiss that goes on once the stove is fully on is a leak.

Over-tightening to stop a leak. Hand tight only. MSR and Jetboil both say more force can damage the seals and cause the leak you were trying to stop.

Leaving the can on in the cold. The O-ring stiffens below freezing, which makes a frosty night the worst time to rely on it.

What this answer does not cover#

This page covers screw-on canisters with the EN 417 valve and the stoves that fit them, both upright and on a hose. It reads three manuals and two support articles from those makers, plus Which?. Other makers' manuals may word things differently; your own stove's manual is the rule for your stove. It does not cover 1 lb propane cylinders, butane cassettes or large propane tanks, which use different valves, so the advice here does not carry across. No maker publishes how fast a joined stove leaks or how much gas each unscrewing costs, so neither figure is given here; the gram sums are arithmetic, and the weighing test is how to find your own number. A stove that passes the soapy water test today can fail later, because O-rings wear, so check the seal each time you connect, and never light a stove in a tent, a car or any closed space.

Frequently asked questions#

Should you disconnect a gas canister from a camping stove after use?#

Yes. MSR, Jetboil and Primus all tell you to unscrew the canister once you have finished cooking and the burner is out. MSR says wait 5 minutes for the stove to cool first, and Jetboil adds that you should refit the plastic cap. MSR's manual warns that storing the two joined "may cause fuel to leak and cause fire".

Can I leave my canister on the stove overnight?#

The maker of MSR stoves says no. Its support article says to store the canister detached "even when camping overnight or between breakfast, lunch and dinner". It describes the slow leak as "not enough to cause harm" but enough to run you low on fuel. In frost the O-ring stiffens, which makes overnight the worst time to leave it on.

Is it OK to leave the canister attached between pots of water?#

Yes, because that is still one cooking session. The manuals' order is connect, cook, turn off, let it cool, then unscrew, so boiling a second pot before you turn off is part of the same use. Unscrew once the whole meal is done and the stove has cooled.

Do you lose gas every time you unscrew a canister?#

A little. Cascade and MSR both say a small amount escapes when you attach or detach, and that it is normal. One gram of gas is about 0.4 litres of it at room pressure, enough to boil about 55 mL of water. Weigh the can before and after ten unscrewings to find your own figure.

Does turning off the stove stop the canister leaking?#

It stops gas reaching the burner, but it does not close the canister. With the stove screwed on, the canister's valve is held open, and the gas is held back by the stove's O-ring and control valve. Which? puts it simply: while the cartridge is screwed in, "there's a route for the gas to get out".

Can you pack a Jetboil with the canister attached?#

Jetboil says no. Its Flash manual says "Always disconnect fuel canister after use" and again "before storing the stove", then refit the plastic fuel cap. The canister can still pack inside the pot; it just should not be screwed into the burner, where knocks in the pack bear on the valve threads.

What is a Lindal valve?#

It is the threaded valve on top of a screw-on gas canister, the type set by the EN 417 standard. A stem in the middle is held shut by a rubber seal. Screwing a stove on presses the stem in and lets gas out, and unscrewing lets it close again. It should seal itself, but a dirty valve can leak, and knocks can damage the thread.