US M40 Protective Mask

US M40 Protective Mask, Respirator, Gas Mask used by the US Army from the 1990s until it was phased out a few years ago in favour of the Avon M50. The M40 was a return to traditional mask design by the USA, after using the M17 Cheek filter mask previously for around 40 years, the XM40 designed in the 1980s eventually went into service a decade later as the M40, using NATO 40mm filters. The mask itself is made from silicone rubber so needs a second skin protective butyl cover to work against blister agents.