An apparatus used to assure adequate oxygen for life support; or, a device worn over the nose and mouth to protect the respiratory tract against airborne contaminants present in the welding atmosphere. Air-supplied respirators or face masks are generally preferred. and air-supplied welding helmets are available commercially.
Filter-type respirators, approved by the U.S. Bureau of Mines for metal fumes, give adequate protection against particulate contaminants that are less toxic than lead, provided they are used and maintained correctly. Filter-type respirators are not recommended for general use because of the difficulty in assuring proper use and maintenance. They will not protect against mercury vapor, carbon monoxide, or nitrogen dioxide.
For these hazards an air-supplied respirator, hose mask, or gas mask is required.