Asphyxia can injure or kill people. This sometimes happens during suicide, torture, and in warfare. It can also be used as a capital punishment. It is also sometimes used nonfatally in martial arts, combat sports, and in some types of sex play. Because the need to breathe is controlled by the amount of carbon dioxide in the blood, some victims may not experience an urgent need to breathe and may remain unaware of the shortage of oxygen in their body.