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Figure. Prototype mask. A) Side view, B) Face side. This mask
consisted of 1 outer layer (≈37 cm × 72 cm) rolled and cut as in
panel B with 8 inner layers (<18 cm2) placed inside
(against the face). The nose slit was first placed over the bridge of
the nose, and the roll was tied below the back of the neck. The area around
the nose was adjusted to eliminate any leakage. If the seal was not tight,
it was adjusted by adding extra material under the roll between the cheek
and nose or by pushing the rolled fabric above or below the cheekbone.
Tie b was tied over the head. A cloth extension was added if tie b was
too short. Finally, tie c was tied behind the head. The mask was then
fit tested.
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