Quantitative fit testing is done by probing the mask so a machine can scientifically prove that there are no leaks in the mask and that the wearer is properly protected. The individual wearing the mask will have to go through a series of simple movements and exercises to ensure that the respirator remains sealed to the face during common movements. Quantitative testing is the preferred form of testing for environments involving hazardous viral or airborne exposures. The individual wearing the respirator must remove any facial hair that lies where the seal has contact with the face.