40 CFR §60.122a

1. (a)On and after the date on which the performance test required to be conducted by § 60.8 is completed, no owner or operator subject to the provisions of this subpart shall discharge or cause the discharge into the atmosphere from a blast (cupola) or reverberatory furnace any gases which:
   1. (1)Contain PM in excess of 10 milligrams per dry standard cubic meter, mg/dscm (0.0044 grains per dry standard cubic feet, gr/dscf).
   2. (2)Exhibit opacity greater than 5 percent.
2. (b)On and after the date on which the performance test required to be conducted by § 60.8 is completed, no owner or operator subject to the provisions of this subpart shall discharge or cause the discharge into the atmosphere from any process fugitive emissions source any gases which:
   1. (1)Contain PM in excess of 4.9 mg/dscm (0.0021 grains per dry standard cubic feet, gr/dscf).
   2. (2)Exhibit opacity greater than 5 percent.
3. (c)The PM and opacity emissions standards specified in paragraphs (a) and (b) of this section apply at all times, including periods of startup, shutdown, and malfunction.