This publication lists devices and instruments certified by NIOSH as of December 31, 1989, for the control and evaluation of occupational hazards. In addition to lists of certified products, this publication contains tables of useful information concerning certified coal mine dust personal sampler units and respirators, updates the lists of approval applicants, and lists some of the more common cautions and limitations for specific respirator classes. The types of respiratory protective devices listed include self contained breathing apparatus, gas masks, supplied air respirators, particulate respirators, chemical cartridges, and powered air purifiers. Respirators are listed by approval class and general cautions and limitations for each approval class are listed. Names and addresses of manufacturers and distributors are included.