Reducing smoke and where to sit

Wood does not burn directly. When heated, it gives off combustible gases, and it is these gases that burn in the flames. If there is enough oxygen and the temperature stays high enough, they burn almost completely into invisible exhaust gases. If either is missing, part of the gases escape unburned and cool down – visible smoke forms.

Wet wood is the most common reason. The water inside must evaporate first, and that takes a lot of heat. The fire stays cooler, and the steam mixes with unburned gases to form dense, whitish-grey smoke. The second reason is a lack of air: a large, tightly stacked pile of wood smothers itself. Green leaves, rubbish and plastics make it even worse.

Where the smoke goes is decided by the wind. In calm weather, smoke collects in hollows. During a so-called inversion – cold air lying near the ground beneath warmer air – it cannot rise and hangs over the surroundings like a lid.

Use only dry, seasoned and split wood. A simple clue: if the wood hisses or foams at the ends when it is in the fire, it is too wet. Split wood dries better and catches fire more easily than round pieces with bark.

A small fire with good draught burns cleaner than a large, smothered stack. Add wood bit by bit instead of throwing a lot on at once, and leave air between the pieces. Never use leaves or greenery to “damp down” flames – that creates a great deal of smoke.

Sit across the wind direction, not in the smoke plume. If the wind shifts, you move. Children and sensitive people sit on the windward side, i.e. where the wind comes from.

Smoke strains the airways as well as the heart and circulation. People with asthma, lung or heart disease, pregnant women, older people and children should avoid smoke exposure. Anyone who develops severe breathing difficulty needs help: call the local emergency number (112 in the EU).

Never burn rubbish, plastics or painted, coated or treated wood. This produces toxic gases that you cannot always smell. A campfire is not a rubbish bin.

The most treacherous danger is carbon monoxide. It is invisible, odourless and can be fatal. Outdoors it disperses; in tents, vehicles and enclosed rooms it builds up – even from embers that hardly smoke any more. So never bring a pot of embers into a tent for warmth. And as always: check local rules and wildfire danger beforehand.

In residential areas, the smoke decides a lot about whether a garden fire is pleasant for everyone. Watch the wind direction, open windows and the neighbours' washing on the line. If the smoke is a nuisance, make the fire smaller or put it out. That is not only polite but also avoids trouble.

There is no completely smoke-free wood fire. A stove produces much less smoke and is a good alternative if it is only about cooking. For a signal fire, by contrast, smoke is made deliberately so that you are seen – that is a separate case with its own rules.