DHHS NIOSH Publication No. 2005-149. 5th printing of the 1997 edition, Spetember 2005, revised to include updated sampling and analytical methode, updated DOT identification and guide numbers, recommendations regarding conact lens use, expanded recommendations for the selection of measurement methods, current exposure limits, guidelnes for selecting respirators in table 4, the new NIOSH carcinogen policy in Appen. A, and expanded synonym and trade name index. Intended as a source of general industrial hygiene information for workers, emplyers and occupational health professionals.