| 摘要 |
A protective facial mask covering the oral and nasal cavities. It slips over the user's head and comprises a single generally cylindrical, generally tubular, piece of an expandable impervious material open at each end. Two diametrically opposed ear slots and an opening below and extending between the ear slots hold the mask in place and provide for better conformity to the user's head. A filtered breathing cannula on the interior of the mask allows air to enter the nasal cavity only. |
