| 摘要 |
<p>A power assisted respirator comprises a facepiece for covering at least the nose and mouth of the wearer which has an outlet provided with a one-way exhale valve which is openable to permit air to flow out of the facepiece when a predetermined pressure P is established within the facepiece. A pump unit supplies air to the space within the facepiece. The pump unit may be connected to an inlet of the facepiece by a flexible hose or may be mounted directly on or in the facepiece. A filter canister is connected to the inlet of the pump means for filtering air supplied to the facepiece. A one-way inlet valve is provided in the path of air flowing from the pump unit to the facepiece and a pressure sensor is provided for sensing the pressure of air in the region of the pump unit inlet for causing deenergisation of the pump unit when the pressure in the region of the pump unit inlet exceeds a predetermined level. The operating parameters of the pump of the pump unit and the exhale valve are selected so that the pressure within the facepiece at which the exhale valve will open slightly exceeds the pressure at the outlet of the pump which will cause the pump to cease or substantially cease operating effectively.</p> |
