The deadliest type of gangrene, gas gangrene, can potentially kill a person within 48 hours of developing if left untreated, writes WebMD. Other types of gangrene can eventually cause death, but they do not progress as quickly as gas gangrene.
Gas gangrene is a condition that results from an infection deep within the body, writes WebMD. This infection is usually due to a traumatic injury, and members of the Clostridia family of bacteria cause it. The bacteria involved in gas gangrene release large amounts of gases and toxins into the body as they grow, resulting in gray areas of skin around the gangrenous area that may crackle when pressed on due to the internal pressure of the gas. It is this release of toxins and gases that make gas gangrene so rapidly deadly if left untreated.