For the past several years, the Bureau of Mines has been actively engaged in developing two new oxygen self-rescuers through research contracts with private industry. These new oxygen self-rescuers are designed to be carried by a miner while he is at work and are used during emergency escape supplying high-purity oxygen to the user and, at the same time, absorbing carbon dioxide (co2). The first of the two new self-rescue breathing devices is a 10-minute, self- contained apparatus developed by the Mine Safety Appliance Company Size and weight of the unit are comparable with those of the currently used self-rescue devices. The second device, designed and developed by Lockheed Missiles and Space Corp., is a 4.5-Lb package that supplies 1 hour of oxygen to the miner. Both devices have a canister that contains the oxygen-producing and co2-absorbing potassium superoxide chemical, a breathing bag, a bite-type mouthpiece, noseclip, goggles, and hoses connecting the canister and mouthpiece. When needed in an emergency, the miner removes the outer protective cover and dons the unit. For both devices oxygen is immediately available once the mouthpiece is placed in the mouth.