In 1978, the National Institute of Occupational Safety and Health (NIOSH) and the Department of Labor produced the original Pocket Guide to Chemical Hazards. It was developed to make technical information on the 380 substance-specific draft standards developed by the Standards Completion Program available to workers, employers, and occupational health professionals. The guide is updated periodically to reflect new data on the toxicity of various substances and any changes in the exposure standards or recommendations. This revision of the NIOSH pocket guide presents specific information and data in an abbreviated tabular form for 677 chemicals and substance groupings, such as manganese compounds, tellurium compounds, and inorganic tin compounds. It includes updated sampling and analytical methods, updated Department of Transportation (DOT) identification and guide numbers, revised conversion factors, current exposure limits, guidelines for selecting “Part 84” respirators, the new carcinogen policy in Appendix A, an expanded synonym and trade name index, and minor technical changes since the June 1994 edition. For each chemical listed, 11 specific types of information are provided and include: (1) chemical name, structure/formula, Chemical Abstracts Service (CAS) and Registry of Toxic Effects of Chemical Substances (RTECS) Nos., and DOT ID and guide Nos.; (2) synonyms, trade names, and conversion factors; (3) exposure limits; (4) immediately dangerous to life or health (IDLH); (5) physical description; (6) chemical and physical properties; (7) incompatibilities and reactivities; (8) measurement method; (9) personal protection and sanitation; (10) recommendations for respirator selection-maximum concentration for use (MCU); and (11) health hazards including route, symptoms, first aid, and target organs. Appendices A-G and indexes