Banking a fire overnight

Embers are burning wood without a flame. They need oxygen to keep glowing – the more air, the faster they burn up. A layer of ash works in two ways: it lets only a little air reach the embers, and it holds the heat in like an insulating blanket. The embers therefore burn very slowly.

A thick, dense log on the embers can also serve as a slow fuel reserve. It gradually chars under the ash and holds the heat. In the morning, ideally, a core of hot embers is left that quickly forms flames again with fresh tinder and air. There is no guarantee, though – sometimes the embers have gone out by morning.

Today, banking embers makes sense mainly with wood stoves and ranges. There the embers burn in a closed firebox of metal or stone, and the air supply can be reduced according to the manufacturer's instructions. In a fixed camp with a fire watch, it can also save ignition sources and tinder.

Outdoors, the safe standard rule is different: the fire is put out completely before sleeping. An unattended campfire in the forest, in wind, drought or during a fire ban is out of the question. Where you are required to put fires out before sleeping, that applies without exception. And never bring embers into a tent, vehicle or a room without a stove.

First you need a good, strong bed of embers. A few scattered, weak pieces of ember will not last until morning. Rake the embers and remaining wood tightly together in the centre of the fire site so they keep each other warm.

The layer of ash must be thick enough that no flames are visible any more. If it is too thin, the fire can flare up again, especially if the wind picks up. If, on the other hand, the embers are buried completely airtight, they suffocate. It takes some experience to find the right amount – so practise first under supervision and in a safe fire site.

In the morning, brush the ash off carefully without breaking up the embers. Put fine tinder and thin wood directly on the hottest spot and blow gently and evenly. Keep your face and hair a little to the side in case ash or sparks swirl up.

A banked fire outdoors is an unattended fire. Wind can blow the ash away, fan the embers back up and carry sparks into dry grass – a wildfire can start this way in the middle of the night while everyone is asleep. So outdoors the rule is: either assign a watch that checks at short intervals and has extinguishing water ready, or put the fire out completely.

Embers give off carbon monoxide, an invisible, odourless gas that can be fatal. Embers, fires and stoves never belong in a tent, vehicle, snow shelter or enclosed room. Anyone running a wood stove overnight should have a working carbon monoxide alarm and use the stove according to the manufacturer's instructions.

Headache, dizziness, nausea or drowsiness near a fire or stove can be warning signs of carbon monoxide. Then get into fresh air immediately, take others with you and call the local emergency number (112 in the EU). Also check the local rules before every fire.

Banking embers was everyday practice at hearths and fireplaces for centuries, when relighting a fire was hard work. To understand why, imagine how much effort it took to start a fire with flint and steel every morning.

For trips there are simpler solutions today: a lighter and matches stored in different places, plus some dry tinder in a waterproof bag. With these, a new fire is quickly made in the morning – without anything having to smoulder unattended during the night.