Improvising a stove windscreen – without overheating the canister

A stove flame heats the air, and this hot air flows along the bottom and sides of the pot. Wind tears this layer of air away and replaces it with cold air – this is called convection. It also pushes the flame sideways so that it partly misses the pot. How much extra fuel this costs depends heavily on the stove, the pot and the wind; there are no fixed figures for it.

A windscreen slows the airflow before it reaches the flame. The hot air stays at the pot longer and the flame burns more evenly. A lid helps as well, because less heat escapes upward with the steam.

But a flame needs oxygen, and the exhaust gases must be able to escape. That is why a gap must remain between windscreen and pot – the entry suggests about a finger's width. If everything is enclosed too tightly, the flame gets too little air, burns poorly, produces soot and creates more carbon monoxide. "As tight as possible" does not mean "as good as possible".

With canister-top stoves the burner sits directly on the gas canister. Here an enclosing windscreen is dangerous, because heat builds up around the canister and the pressure inside rises. The screen may only stand beside the burner, as a half-open arc on the windward side, and must not reach down to the canister. A very large pot that reflects heat back down onto the canister is also a poor idea with these stoves.

With hose-connected (remote-canister) stoves the canister stands some distance away. Here the windscreen can largely enclose the burner – as long as the canister and hose stay outside and the manufacturer explicitly allows it. With alcohol and liquid-fuel stoves a windscreen is often part of the system; here too, what counts is what the instructions say.

So the most important rule is simple: read your stove manufacturer's instructions on windscreens and follow them. Also use only the fuel your stove is built for – no improvised or mixed fuels.

Start with the terrain before you build anything. Behind a boulder, a wall or a bank it is often noticeably calmer already. Your body or a backpack can block extra wind – the backpack at a good distance, though, because it can burn. The ground must be level and non-flammable, such as rock, gravel or bare soil, so the stove cannot tip over.

For a foil wall, fold several layers of foil into a strip a little taller than the flame. Stand it as a half-open arc on the windward side and weigh it down with stones. Multi-layer foil creases less and lasts longer; even so, it tears over time and needs replacing.

Never leave the stove unattended. In gusts, watch the flame: if it shoots out sideways from under the pot or flickers hard, improve the screen or wait for the gust to pass. With canister-top stoves, keep checking by hand that the canister stays cool.

Canister: if it gets warm, that is a warning sign. Turn the stove off if you can do so safely, remove the windscreen and let everything cool before you carry on cooking with a more open screen. A canister must never be wrapped, covered or surrounded by hot stones.

Carbon monoxide: stoves are run outdoors only, never in a tent, vestibule, car or living space – not even "just for a moment" because of the wind. Carbon monoxide is odourless and invisible. Headache, dizziness or nausea while cooking can be warning signs: get into fresh air at once and if symptoms continue call the local emergency number (112 in the EU).

Burns and fire: foil and stones by the stove get hot and stay hot for a while. Do not touch them with bare hands and keep children away. Alcohol flames are almost invisible in daylight – never refill an alcohol stove while it is burning or still hot. Do not use flammable materials such as cardboard or fabric as a windscreen, and watch out for dry grass nearby. When fire danger is high, stoves may be restricted too – check local rules.

Try your windscreen first on a windy day in the garden, on a stone-paved patio or at a barbecue spot – not only once you are on a trip. Boil the same amount of water once without and once with the screen and compare how long it takes. That way you see for yourself how much the screen helps.

Practise the canister check at the same time: after a few minutes, put your hand on the canister. If it stays cool, your set-up is fine. If it becomes noticeably warm, the screen is too tight or too close.

A pre-folded foil strip weighs almost nothing and packs flat inside the pot. Once you have found a shape that suits your stove and that the manufacturer allows, always take it with you.