Each respirator user must receive fitting instructions that include demonstrations and practice on how the respirator should be worn, how to adjust and how to determine if the respirator fits properly. Although respirators are designed for maximum efficiency, they cannot protect the wearer without a tight seal between the facepiece and wearer. Beards and other facial hair can substantially reduce the effectiveness of a respirator. The absence of dentures can seriously affect the fit of a facepiece. To assure proper protection for a facepiece, it must be checked by the wearer each time the respirator is put on.
Corrective lenses worn by employees also present a problem when fitting respirators.
Special mountings to hold corrective lenses inside full facepieces are available. If corrective lenses are needed, the facepiece and lens must be fitted by a qualified individual to provide good vision, comfort, and proper sealing. Contact lens should not be worn while wearing a respirator in a contaminated area. Foreign bodies or contaminants that penetrate the respirator may get into the eyes and cause severe discomfort compelling the wearer to remove the respirator. Full facepiece and half-mask respirators have different fitting characteristics.