Compressed gas refers to gas that is stored under high pressure in a container, which reduces its volume. This process allows for the storage and transportation of gases like oxygen, nitrogen, and helium in a more manageable form. When released, the gas expands rapidly, returning to its original volume. Compressed gases are commonly used in various applications, including welding, medical equipment, and aerosol products. Safety is crucial when handling compressed gases, as they can pose risks such as explosions or asphyxiation if not managed properly. Proper storage and usage guidelines help mitigate these hazards.