A respirator test facility using Refrigerant 12 as a challenge gas has been developed. More than 6000 people have received training in the effective use of mouthpiece respirators. Leakage is determined by the use of a halide detection meter analyzing the exhaled breath. The facilities have been used to provide training and quantitative fit testing for practically all types of respiratory protective equipment. An actual use investigation was made to determine the suitability of the mouthpiece respirator for use in a chlorine producing plant work situation. The mouthpiece respirator was compared with a group of half-face respirators. A clear distinction was made: the half-face respirator offered less protection than the mouthpiece respirator.