Section 60.122 - Standard for particulate matter(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) Contain particulate matter (PM) in excess of 50 milligrams per dry standard cubic meter, mg/dscm (0.022 grains per dry standard cubic feet, gr/dscf).(2) Exhibit 20 percent opacity or greater.(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 pot furnace any gases which exhibit 10 percent opacity or greater.39 FR 9317, Mar. 8, 1974, as amended at 40 FR 46259, Oct. 6, 1975; 88 FR 80610, Nov. 20, 2023