A self-sufficient breathing unit that permits freedom of movement, unencumbered by air hoses. It offers the wearer respiratory protection in atmospheres that are either oxygendeficient or too highly toxic to permit the use of gask masks or respirators. The oxygen or air is supplied in compressed form or by chemical generation, and the wearer's exhalations are either purified for re-use or released to the surrounding atmosphere. The equipment is devised to afford protection for special lengths of time, in accordance with the standards set by the Mine Safety and Health Administration. The 2-h apparatus is used for mine rescue and recovery operations; shorter period apparatus is available for industrial uses and auxiliary equipment.