OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force. OSHA's former exposure limit for ammonia was 50 ppm as an 8-hour TWA. OSHA proposed to revise this limit to 25 ppm TWA and to add a 35-ppm 15-minute STEL, based on the limits established by the ACGIH.