Abstract: A portable negative pressure respirator shell comprising a plurality, typically two, of rigid shell sections co-operable to provide an open ended shell for a patient's torso. Variable resilience flexible sealing lips are disposed along the top and bottom edges of the shell sections to aid in providing an airtight engagement with the body surface of the patient on the application of a negative pressure to said chamber, which engagement may be relieved by a suitable greater pressure in said chamber. The sealing lips are advantageously of reducing thickness and directed inwardly. Also disclosed are a power unit and reciprocatory valve for use with the respirator.