40 CFR §63.1157

1. (a)Pickling lines. No owner or operator of an existing affected continuous or batch pickling line at a steel pickling facility shall cause or allow to be discharged into the atmosphere from the affected pickling line:
   1. (1)Any gases that contain HCl in a concentration in excess of 18 parts per million by volume (ppmv); or
   2. (2)HCl at a mass emission rate that corresponds to a collection efficiency of less than 97 percent.
2. (b)Hydrochloric acid regeneration plants.
   1. (1)No owner or operator of an existing affected plant shall cause or allow to be discharged into the atmosphere from the affected plant any gases that contain HCl in a concentration greater than 25 ppmv.
   2. (2)In addition to the requirement of paragraph (b)(1) of this section, no owner or operator of an existing plant shall cause or allow to be discharged into the atmosphere from the affected plant any gases that contain chlorine (Cl2) in a concentration in excess of 6 ppmv.