Fire

Warmth is third.

1. Making water safe. A rolling boil kills everything living in water, needs no dose and no timer, and diarrhoeal disease is the largest killer in every collapse on record. See the water guide.
2. Not dying of cold. Hypothermia kills in hours, not days. Wet and windy at 10 °C is more dangerous than dry and still at −5 °C, because water conducts heat from the body roughly 25 times faster than air.
3. Cooking. Heat makes starch digestible and destroys the parasites in meat and fish. It is also the difference between eating acorns and not.
4. Light, and the working day. Without fire the usable day ends at dusk for half the year.
5. Signalling. Smoke by day, flame by night.
6. Everything after tier 0. Charcoal, pottery, lime, glass and metal are all fire with a container around it. The charcoal clamp is the first of them.

Reach for them in this order. The romance of the list runs the opposite way to its reliability.

Tinder is not "small dry stuff". It is the specific set of materials that ignite between about 150 and 250 °C and present enough surface area to catch a spark that lasts under a second.

The distinction that matters in the field is between spark tinder — takes a ferro-rod or flint spark directly — and flame tinder, which needs an existing flame or a glowing ember blown to life. Most "tinder" people collect is the second kind, which is why the spark keeps dying.

Collect it dry, in quantity, and carry it. Every one of the materials below can be gathered on a good day and kept for months.

Fire fails at the joins. Tinder to kindling, kindling to fuel — each transition needs the next size to already be there, dry, within reach. Prepare four grades before you make a spark:

1. Tinder — a bundle the size of two fists.
2. Matchstick — dead twigs that snap rather than bend. Enough to fill both hands.
3. Finger to thumb. A double armful.
4. Wrist to arm. As much as you can gather before dark.

The snap test is the whole moisture test: dead wood that snaps cleanly is dry; wood that bends is wet and will not burn. Take it from standing dead trees and from branches still attached, never from the ground — ground wood has been wicking moisture for as long as it has been lying there.

Seasoning matters more than species. Freshly cut wood is 45–60% water by weight; seasoned wood is 15–20%. Green wood spends most of its energy boiling its own water, which is why it hisses, smokes and will not hold a bed of coals.

A fire lay is an airflow decision, not an aesthetic one. Fire needs air entering underneath and heat concentrated where the next piece has to catch.

• Teepee. Fastest to flame, burns fast, collapses. The lay for lighting, not for keeping. Use it to get going and let it fall into a bed.
• Log cabin. Square stack, stable, long-burning, makes a deep coal bed. The cooking and overnight lay.
• Lean-to and star. A windbreak log with kindling leant against it; or long logs pushed inward as they burn. Both need almost no cutting, which matters before you have an axe.
• Long fire. Two parallel logs a hand's width apart, fire between them, pots resting across. The working fire.
• Dakota fire hole. Two connected pits — a fire chamber and an air shaft angled into its base. Burns hot, uses little wood, shows almost no flame and little smoke, and is invisible at a distance. The one to build when concealment or wind matters. Never in peat or dense root mat, where it starts an underground fire that can burn for months.

A reflector — a stacked log wall or a rock face on the far side — roughly doubles the useful heat reaching a person, and costs ten minutes.

Anyone can light a fire on a dry day. The procedure below is for the day that actually matters, and every step of it is about getting at wood that the rain has not reached.

1. Get off the ground. Build a platform of finger-thick sticks, two layers, crossed. A fire laid on wet ground spends its first ten minutes boiling the ground.
2. Take standing dead wood only. Branches still attached to a dead trunk, or a dead standing sapling. Anything from the forest floor is a sponge.
3. Split everything. The outside of a log is wet; 20 mm in, it is dry. Baton the wood down with a knife and a striking stick, and work from the middle outward.
4. Make feather sticks from those dry cores. This is the point of the technique — it converts a wet log into tinder.
5. Use fatwood or birch bark if either is present. Both burn wet.
6. Build it complete before you strike, with a hand shielding it, and a body between it and the wind.
7. Dry the next grade over the flame as it burns. From this point you are always drying the fuel you will use in ten minutes' time.

In continuous rain, roof it — a slab of bark, a stretched garment, a lean-to of boughs. Fire that is lit and then rained out has cost you the tinder as well as the time.

The purpose of the first fire is the second fire. A group that relights from scratch every morning is spending an hour a day on a problem it has already solved.

Banking, at night. Rake the coals into a compact pile — depth matters more than area. Lay one or two large, dense rounds (oak, ash, beech) on top, unsplit, bark outward. Cover the whole pile with 50–100 mm of fine ash. Ash is an insulator; it starves the coals to a slow smoulder without putting them out. In the morning, scrape the ash aside, put shavings on the exposed coal and breathe. A properly banked bed holds 8–14 hours, and longer in a fire pit with stone sides.

Carrying fire. A dry chaga or a King Alfred's cake lit at the edge and packed in a bark tube with a little air holds an ember for hours. A horn or a clay pot with ash below and above the coal does the same. This is how fire travelled before anyone could make it on demand, and it is far less work than remaking it.

Naming a keeper. Say out loud who is responsible for the fire tonight. Fires go out because responsibility was assumed, not assigned.

Carbon monoxide. It is colourless, odourless, non-irritating, and it is the reason fire indoors kills people who did everything else right.

Any incomplete combustion produces it. Charcoal and a smouldering, oxygen-starved fire are the worst offenders, because they produce a great deal of CO and almost no smoke to warn you — the warning sign most people are relying on is absent precisely when the danger is highest. CO binds to haemoglobin roughly 250 times more readily than oxygen, so a small concentration in the air becomes a large fraction of the blood's carrying capacity.

The symptoms are the problem: headache, nausea, dizziness, confusion — indistinguishable from exhaustion, altitude, dehydration or a bad night. Confusion means the person cannot be relied upon to save themselves, and drowsiness follows. In a shelter, everyone is affected at once, so nobody notices that everyone is impaired.

Rules that have no exceptions:

• Never burn charcoal or a stove inside a tent, vehicle, snow shelter or unventilated room. Not briefly, not to take the edge off, not while awake.
• Ventilate high and low. An opening at floor level and another at the roof gives a through-draught. One small gap is not ventilation.
• Never sleep with an unvented fire indoors. Bank it outside, or accept the cold.
• If two or more people have a headache at the same time in the same shelter, get everyone into open air first and discuss it afterwards. The shared symptom is the diagnosis.
• Treatment is fresh air and, if available, high-flow oxygen. Recovery is slow — CO's half-life in blood is around 4–5 hours breathing ordinary air.