Also known as caisson disease, this affects workers operating in compressed-air environments, such as underwater divers and workers in caissons (such as an ammunition wagon, a chest of explosive materials, or a strong case for keeping out the water while the foundations of a bridge are being built; derived from the French caisse, meaning case or chest). Its chief symptoms are pains in the joints and limbs (bends); pain in the stomach; headache and dizziness; and paralysis. Sudden death may occur. The condition is caused by the accumulation of bubbles of nitrogen in different parts of the body, usually because of too-rapid decompression when the worker returns to normal atmospheric pressure – a change that must be made gradually.