Designed to prevent the inhalation of dust. Two types of filtering systems are available : a Mechanical Type which filters fumes and dust through a filter cartridge, and an Electrostatic Type which collects fumes and dust over the filter by static electricity. It must be noted that these masks are not effective for poisonous gases or vapours. Also to avoid risk, it must never be used in circumstances where the Oxygen (O2) concentration is lower than 18 %.