California Code, Labor Code - LAB § 6625

(b) The filing of a petition for, or the pendency of, reconsideration of a final order or decision involving a citation classified as serious, repeat serious, or willful serious does not stay or suspend the requirement to abate the hazards affirmed by the decision or order unless the employer demonstrates by a preponderance of the evidence that a stay or suspension of abatement will not adversely affect the health and safety of employees. The employer must request a stay or suspension of abatement by filing a written, verified petition with supporting declarations within 10 days after the issuance of the order or decision.