42 CFR 84.75 - Half-mask facepieces, full facepieces, mouthpieces; fit; minimum requirements.
(1) By providing more than one facepiece size; or
(2) By providing one facepiece size which will fit varying facial shapes and sizes.
(b) Full facepieces shall provide for the optional use of corrective spectacles or lenses which shall not reduce the respiratory protective qualities of the apparatus.
(c) Apparatus with mouthpieces shall be equipped with noseclips which are securely attached to the mouthpiece or apparatus and provide an airtight seal.
(d) Facepieces shall be designed to prevent eyepiece, spectacle, and lens fogging.