Products which have been certified by NIOSH as of December 31, 1988 for use in protecting workers from hazardous working conditions and for use in providing reliable measurements of working environments were listed. Information was also included concerning specific coal mine dust personal sampling units and respirators, approval applications, and various cautions and limitations which must be considered when selecting respirators. The design of self contained breathing apparatus for entry into and escape from work areas, for escape only and to be used as a combined self contained breathing apparatus and a supplied air respirator was described. Gas masks were described for use against ammonia (7664417), chlorine (7782505), sulfur-dioxide (7446095), acid gases, organic vapors, carbon-monoxide (630080), pesticides, and other gases and vapors. Types of supplied air respirators described include Type-C continuous flow, pressure demand and demand, Type-CE continuous flow abrasive blasting, Type-A, and Type-B. Particulate respirators were described for single use; for use against dust and mists; for use against dusts, fumes and mists; and for high efficiency purposes. Chemical cartridges effective against ammonia, methyl-amine, chlorine, hydrogen-chloride, chlorine, sulfur-dioxide, organic vapor, paints, lacquers, enamels, pesticides, vinyl-chloride, and other gases and vapors were considered. Powered air purifiers were also described. Names and addresses of manufacturers and distributors were listed.