The Occupational Safety and Health Administration has established a time-weighted average (TWA) standard of 500 ppm (2,900 milligrams per cubic meter of air [mg/m3]) for an 8-hour workday, 40-hour workweek to prevent nervous system and skin damage. NIOSH has published a recommended exposure limit of 350 mg/m3 TWA for a 10-hour workday and a ceiling level of 1,800 mg/m3 (15-minute sampling period). The American Conference of Governmental Industrial Hygienists has recommended a threshold limit value TWA of 100 ppm (525 mg/m3) for an 8-hour workshift.
