half-mask

Short definition from Wiktionary

Noun

1. 1
   A mask covering half the face: A dust mask.
2. 2
   A mask covering half the face: A filtering facepiece respirator.
3. 3
   A mask covering half the face: An elastomeric respirator.
4. 4
   A mask covering the eyes and perhaps the forehead or nose, but not the mouth
5. 5
   A mask covering the eyes and perhaps the forehead or nose, but not the mouth: A half-face diving mask.