This publication listed products certified as of December 31, 1990 for use as safe personal protective devices and reliable industrial hazard measuring instruments. NIOSH has been authorized to develop improved performance regulations, test and certify such devices. The report contained tables of useful information concerning certified coal mine dust personal sampler units and respirators, updated the lists of approval applicants, and listed some of the more common cautions and limitations for specific respirator classes. The names and addresses of manufacturers and distributors were included for coal mine dust personal sampler units. Types of self contained breathing apparatus described include open circuit pressure demand, open circuit demand, closed circuit, closed circuit pressure demand for entry into and escape, for escape only, or combined self contained and supplied air respirators. Protective devices for use during exposure to the following agents were discussed: ammonia (7664417), chlorine (7782505), sulfur-dioxide (7446095), acid gases, organic vapors, carbon-monoxide (630080), pesticides, dusts, mists, methylamine (74895), hydrogen-chloride (7647010), paints, lacquers and enamels, vinyl-chloride (75014), and other gases and vapors.