Caves, tunnels and old mines: stay out

At the surface the wind keeps the air constantly mixed. Underground that is missing. In old tunnels oxygen can be used up by rust, rotting timber or the rock itself. Heavy gases such as carbon dioxide collect in deep spots and hollows, and other gases can seep out of the rock. Many of them are invisible and odourless. Lack of oxygen can cause light-headedness and confusion before you notice anything is wrong – and then the strength to get back out is often missing.

Mines were built for a certain period of use. Timber supports rot over decades, rock is loosened by water and frost, and roofs can cave in without warning. Vertical shafts can be very deep; their openings are sometimes hidden by plants, debris or rotten covers, and their edges can give way. Many old tunnels are also partly flooded.

Natural caves have different but equally serious dangers. Passages branch into mazes, and without light all orientation is lost. Rain at the surface can flood cave passages within a short time, even if it was dry when you went in. A well-known example is the Tham Luang cave in Thailand, where in 2018 a youth football team was trapped by water after rainfall and could only be freed through a complex international rescue operation.

Many accidents begin with the thought “just a few metres”. Yet the first metres of a tunnel are often especially unstable, because frost and water act most strongly there. Bad air can be present close to the entrance, and shafts can lie just round a bend. A phone torch is not enough to spot these dangers, and its battery soon runs flat.

Tunnels and caves are not a good choice as shelter in a thunderstorm or rain either. Water can flow in, rock can come loose, and in a thunderstorm cave entrances can even be dangerous. A shallow rock overhang can give brief shelter but carries a rockfall risk; a building or vehicle is better.

Curiosity is not a bad thing. For caves there are show caves with safe paths and lighting, and caving clubs that train newcomers and take them on trips. For mining there are show mines where, with a guide and safety equipment, you can experience how people used to work underground.

Do not enter abandoned mines, tunnels or shafts, and never cross barriers. Outside, too, keep away from shaft openings, hollows and holes in the ground in mining areas, because their edges can give way. Anyone who finds open shafts or damaged barriers reports them to the local council or the responsible authority.

If someone has had an accident or is missing in a cave or tunnel, do not go in yourself to search. Especially with bad air, helpers often become victims themselves. Call the local emergency number (112 in the EU), note exactly where the entrance is and wait there for the rescue services. Cave and mine rescue are specialist tasks with their own equipment and training.

With children and teenagers it is worth talking openly about why old mines and abandoned sites are not adventure playgrounds. Bans on their own often work less well than explanations: invisible gases, collapsing roofs, hidden shafts. Those who understand the reasons are more likely to make the right decision themselves.

The US mine safety agency MSHA has warned for years with its “Stay Out–Stay Alive” campaign against entering abandoned mines. It names collapse, shafts, bad air and water as the main dangers – the same dangers exist in old mining areas worldwide.

Caves and tunnels are often winter roosts for bats. In the EU all bat species are strictly protected. If they are disturbed during hibernation, they use up energy reserves they need to survive. That is why some entrances are closed in winter or fitted with grilles that bats can fly through but people cannot walk through.

Caving is a serious hobby and a science with its own training, equipment and safety rules, such as always going in a group and telling someone outside exactly where you are. Anyone interested will find the right way in through a caving club.