Gas mask

Gas mask was a piece of equipment utilized by the Assassin-turned-Templar Shay Cormac, during the 18th century.

The mask was a piece of cloth, which Shay could pull up to cover his face, and protect himself from the harmful effects of poisonous vapors, or the smoke bombs. When not in use, Shay typically kept the mask lowered, using it only in situations where he deemed it necessary, and during his hunts for his former Assassin brethren.

Reference

 * Assassin's Creed: Rogue