This pocket guide produced by NIOSH was designed to provide chemical specific data to supplement general industrial hygiene knowledge. It was produced for use by workers, employers and occupational health professionals. Abbreviations and codes have been extensively used in the guide. The guide provides the chemical name and structure or formula for a compound, the Chemical Abstracts Service Registry Number and NIOSH Registry of Toxic Effects of Chemical Substances Number and Department of Transportation identification number and guide numbers. In the guide there is a list of synonyms, trade names, conversion factors, exposure limits, concentrations deemed to be immediately dangerous to life or health, physical descriptions, chemical and physical properties, incompatibilities and reactivities, measurement method, personal protection and sanitation, recommendations for respiratory selection, route of health hazard, symptoms, first aid, and target organs. The information is provided for 677 chemicals or substance groupings that are found in the work environment. All of the substances for which NIOSH has recommended exposure limits are included along with those with permissible exposure limits as found in the OSHA General Industry Air Contaminants Standards.