A Hyperbaric Chamber (from "hyper" (high) and "baric" (atmosphere)) is a sealed pressurized chamber filled with pure oxygen. It is most commonly used for the treatment of burn victims, although it can also be used to treat anaerobic bacteria that infect open wounds, such as gas gangrene and carbon monoxide poisoning. It is the first treatment for patients suffering from decompression sickness. It can also be used to help persons acclimatate to altitude by encouraging the production of red blood cells. They are often used by athletes who engage in endurance events such as cycling and marathon running to simulate the air pressure at sea level while sleeping when athletes train at altitude.