| 摘要 |
<p>A nasal filter has a pair of members fitting in the nostrils, each member having a central air intake passage with a screen between the front end of the passage and the ambient air. The central passage is surrounded by an annular exhaust channel closed by a one way valve allowing exhaled breath out. A slidable closure plate closes the back end of the air intake passage during exhaling to avoid mixing fresh and vitiated air, the plate being pushed against the end of the channel by the pressure of the exhaled air. An electronic filter powered by a battery to which both members are attached is positioned in the central passage for holding dirt or other particles which may pass through the screen.</p> |
