40 CFR § 60.92
Standard for particulate matter
June 9, 2020
(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 any affected facility any gases which:
(1) Contain particulate matter in excess of 90 mg/dscm (0.04 gr/dscf).
(2) Exhibit 20 percent opacity, or greater.
[39 FR 9314, Mar. 8, 1974, as amended at 40 FR 46259, Oct. 6, 1975]