Cal. Lab. Code § 5005
In any case involving a claim of occupational disease or cumulative injury, as set forth in Section 5500.5, the employee and any employer, or any insurance carrier for any employer, may enter into a compromise and release agreement settling either all or any part of the employee's claim, including a part of his claim against any employer. Such compromise and release agreement, upon approval by the appeals board or a referee, shall be a total release as to such employer or insurance carrier for the portion or portions of the claim released, but shall not constitute a bar to a recovery from any one or all of the remaining employers or insurance carriers for the periods of exposure not so released.
In any case where a compromise and release agreement of a portion of a claim has been made and approved, the employee may elect to proceed as provided in Section 5500.5 against any one or more of the remaining employers, or against an employer for that portion of his exposure not so released; in any such proceeding after election following compromise and release, that portion of liability attributable to the portion or portions of the exposure so released shall be assessed and deducted from the liability of the remaining defendant or defendants, but any such defendant shall receive no credit for any moneys paid by way of compromise and release in excess of the liability actually assessed against the released employments and the employee shall not receive any further benefits from the released employments for any liability assessed to them above what was paid by way of compromise and release.
In approving a compromise and release agreement under this section, the appeals board or referee shall determine the adequacy of the compromise and release agreement as it shall then reflect the potential liability of the released exposure after apportionment, but need not make a final actual determination of the potential liability of the employer or employers for that portion of the exposure being released.
Ca. Lab. Code § 5005