| 摘要 |
<p>The helmet protects the eyes and lungs against noxious gases. It comprises a plastic shell strapped on top of the head and a similar mobile portion attached to it by bellows. This forms a pump, operated by a lever and chin strap. Opening the mouth to breathe pumps air into the space inside the helmet. Closing the mouth separates the pump halves, being spring biased, and air is drawn through the filter in the upper part of the helmet. Used air is expelled through the neck seal. The action prevents strain on the lungs when pulling air through the filter.</p> |
