Cal. LAB § 9061

(a) For purposes of this part, “serious violation” shall have the meaning specified in Section 6432 and, except as provided in subdivision (b), shall additionally include any violation of a standard or special order respecting the use of a carcinogen. (b) A violation of a standard or special order respecting the use of a carcinogen shall not, be a “serious violation” if the employer did not, and could not, with the exercise of reasonable diligence, know of the presence of the violation or if the violation is minor and resulted in no substantial health hazard, as determined by the division.