California Labor Code § 4458

If a member registered as an active firefighting member of any regularly organized volunteer fire department as described in Section 3361 suffers injury or death while in the performance of his duty as fireman, or if a person engaged in fire suppression as described in Section 3365 suffers injury or death while so engaged, then, irrespective of his remuneration from this or other employment or from both, his average weekly earnings for the purposes of determining temporary disability indemnity and permanent disability indemnity shall be taken at the maximum fixed for each, respectively, in Section 4453. Four times his average annual earnings in disability cases and in death cases shall be taken at the maximum limits provided in Sections 4452 and 4702 respectively.