| 摘要 |
The present invention relates to improvements in power assisted positive pressure respirators for use in contaminated atmospheres. The respirator comprises a facepiece 1 having an inlet 3 connected to a pump unit 5 for supplying air to the facepiece which has been filtered by filter means 11 connected to the pump unit inlet. The facepiece is also provided with an outlet provided witha one-way valve 2 which is biased to its closed position and is openable when a predetermined pressure above atmospheric pressure is established within the facepiece. To maximise use of the filter means 11, a one-way inlet valve 13 is provided intermediate the pump unit 5 and the facepiece 1, conveniently at the inlet to the facepiece, which is closed during exhalation by the wearer to thereby cause the pump to be placed in a condition in which, although it continues to operate, no or substantially no air is moved thereby, so that during this period, no or substantially no air is drawn through the filter means 11. |
