This publication lists coal mine dust personal sampler units, gas detector tube units, and respiratory protective devices certified by the National Institute for Occupational Safety and Health (NIOSH) as of July 18, 1974. It replaces the previous list (February 1974) and its supplement; the information from which it contains. Future certifications will be listed in supplements to this publication. Use of the terms "approved" and "certified" throughout this publication reflects the applicable regulations. Those regulations issued under authority of the Federal Coal Mine Health and Safety Act of 1969, refer to approval of devices in keeping with the wording of that act. All NIOSH regulations issued under authority of the Occupational Safety and Health Act of 1970 refer to certification of devices and instruments.