They avoid using cotton clothing because once wet, it conducts heat away from the body. These types of clothing allow sweat and water vapor to escape from the skin through the clothing. By keeping warm and dry, mountaineers avoid the dangers of severely chilling their body core, which can lead to hypothermia. For more information on hypothermia and other hazards associated with mountain climbing, see the Mountain Safety section of this article. Mountaineers wear fiberglass or high-strength plastic helmets to protect their heads from falling pieces of rock or ice, as well as from head injuries if they fall themselves.
Mountain climbers use many different tools.
The most basic of these are climbing harnesses, climbing ropes, ice axes, and crampons. Climbers also use a variety of types of hardware to anchor themselves to the mountainside. A climbing harness is an adjustable set of straps that buckle around the waist and thighs of a climber. The harness serves as an anchor for one end of the climbing rope. In the event of a fall, the anchors set in the mountainside halt the fall, and the harness holds the climber tight but does not restrict movement or breathing.