A self-contained breathing apparatus has been developed to provide complete respiratory protection for a miner in an irrespirable atmosphere. The apparatus has the desired features of comfort, reliability, maintainability, and quick-donning capability. The unit is a small, lightweight, one-time-use device that can be readily worn on a miner's belt and is designed to have a shelf life of 5 years and a carrying life of 3 years. It is deployed to the use position in a period of 15 to 30 seconds. The apparatus has a 10-minute service life under escape conditions and a 30-minute service life when the wearer is at rest.