Occupational exposure limits (OELs) for NO2 are set by various organizations to protect workers from harmful exposure. For example, the OSHA has set a permissible exposure limit (PEL) of 5 ppm for an 8-hour time-weighted average (TWA). The ACGIH recommends a threshold limit value (TLV) of 3 ppm as a TWA for a normal 8-hour workday and a 40-hour workweek.
