Emergency poncho from a bin bag

Plastic sheeting is waterproof and airtight. Rain runs off and wind cannot blow through your clothing. That is exactly what makes it valuable in the cold: wet clothing conducts heat away from the body much faster than dry clothing, and wind strengthens this effect. A bin bag over your clothes can therefore noticeably slow cooling from wet and wind.

The downside: your body constantly gives off moisture, and a lot of it when walking. Breathable rain gear lets some of it escape. Plastic cannot. The water vapour condenses on the inside of the plastic and makes clothing damp from within. A loose fit that lets air in at the bottom and the arms eases this a little.

A bin bag is not insulation – it does not warm you by itself. It only holds on better to the warmth already in your clothes, because wind and rain no longer carry it away.

Take a large, heavy-duty bag. Thin bags tear while you put them on or on the first branch. Hold it with the closed bottom up and, a little below the bottom, cut an oval hole the size of your face on one side. The bottom then sits on your head like a hood and your face looks out freely. Without a knife the hole can also be carefully torn.

Cut arm slits at the sides at about shoulder height. If you are only waiting, your arms can stay inside – that keeps you warmer. A cord tied loosely around your waist keeps the bag against your body so the wind does not puff it up like a balloon or blow it into your face.

During breaks and in the cold a dry layer under the bag helps. If you notice you are sweating underneath, slow down or open the bag briefly. And think of your backpack: a second bag inside the pack keeps your sleeping bag and spare clothes dry – often that is even more important than the poncho itself.

Plastic bags can cause suffocation. So without exception: the bag is never pulled over the head, mouth and nose always stay free, and the face hole is big enough. Small children get no plastic bags, not even to play with. Older children only wear an emergency poncho under supervision, with a large face opening and the head free.

Wet clothing under the plastic increases the risk of hypothermia, especially when you stop after exertion. Watch for warning signs such as intense shivering, clumsiness or confusion. Then: find shelter, put on dry clothing, insulate from the ground and, with serious signs, call the local emergency number (112 in the EU).

In strong wind and in brush a bin bag is quickly shredded. Flapping plastic can also block your view. So belt it and make sure nothing blows across your face.

The emergency poncho makes sense in unexpected rain, while waiting outdoors – at a bus stop or for help, say – and as an extra wind layer in an emergency. A bin bag weighs almost nothing, fits in any pocket and can also be a pack liner, a sit mat or a rubbish bag.

It is less suitable for long hikes with a lot of exertion, because you sweat through underneath. In dense brush it tears, and in a storm it flaps. For small children it is off-limits. Anyone who goes out regularly carries proper rain gear and keeps the bin bag as an extra reserve.

Bin bags appear on many emergency and hiking lists because they are so versatile. Military survival manuals have long described how ponchos and plastic sheeting can be used as rain protection, groundsheet or roof.

A light or brightly coloured bag is easier to see in the landscape than a black one – that can be useful if you want to be found. Try the emergency poncho once at home with an old bag: then you know where the hole goes and how big it needs to be.