Breathing gas is a mixture of gases that is safe for humans to inhale. The most common breathing gas is air, which consists mainly of nitrogen and oxygen. In specialized environments, such as underwater or in space, different mixtures are used to ensure safety and efficiency. In scuba diving, for example, divers often use a mixture called nitrox, which has a higher oxygen content than regular air. This helps reduce the risk of decompression sickness. In space missions, astronauts breathe a controlled mixture of gases to maintain their health and support their activities in a low-pressure environment.