gas mask

noun

1. a masklike device containing or attached to a component that filters the air inhaled by the wearer through charcoal and chemicals, for protecting the face and lungs against noxious gases and fumes, as in warfare or in certain industrial processes.

noun

1. a mask fitted with a chemical filter to enable the wearer to breathe air free of poisonous or corrosive gases: used for military or industrial purposesAlso called (in Britain): respirator