Gas gangrene can develop after certain types of surgery or injuries.
Blisters with gas bubbles form near the infected area, accompanied by fever, rapid heartbeat and breathing, and often pain at the infection site.
Symptoms suggest the diagnosis, and imaging tests or culture of a sample taken from infected tissue is usually done.
Treatment involves high doses of antibiotics and surgical removal of dead or infected tissue.

Gas gangrene is a fast-spreading clostridial infection of muscle tissue that, if untreated, quickly leads to death.
Several thousand cases of gangrene occur in the United States every year.
Clostridia thrive when no oxygen is present. That is, they are anaerobes. So they reproduce well in soft tissues that have been severely damaged and in wounds that are very deep. Such tissues have poor blood flow and thus low oxygen levels.
Most clostridial soft-tissue infections, including gangrene, are caused by Clostridium perfringens. Clostridial soft-tissue infections usually develop hours or days after an injury but sometimes take several days to appear.
Other clostridial soft-tissue infections include

Shallow skin infections (cellulitis), which may not be very painful
Deeper infections into fibrous tissue around the muscles called fascia (fasciitis) or muscle (myositis), which usually are painful

Skin infections rarely spread and become serious.
Sometimes the bacteria in soft tissues produce large amounts of gas as a waste product. The gas can form bubbles and blisters in tissue. Often, the infection blocks small blood vessels. As a result, the infected tissue dies, leading to gangrene. The dead tissue enables the clostridial infection to spread even faster. Gangrene is more likely to develop when muscle is infected than when only the skin is infected.