N.J. Stat. § 40A:14-50
"Emergency" as used herein shall include any unusual conditions caused by any circumstances or situation including shortages in the personnel of the paid or part-paid fire department and force caused by vacancies, sickness or injury, or by the taking of accrued vacation or sick leave or both, whereby the safety of the public is endangered or imperiled, as shall be determined within the sole discretion of the officer, board or official having charge of the paid or part-paid fire department and force in any municipality.
In any municipality in which the officer, board or official having charge or control of the paid or part-paid fire department and force has authority, in times of any such emergency to summon and keep on duty any paid members of the paid or part-paid fire department and force for a period or periods of time in excess of the hours of ordinary duty, the governing body may provide compensation for some or all of such emergency duty by any such fireman at his prevailing wage, or at a rate not in excess of 1 1/2 times his prevailing hourly wage rate, which compensation shall be in lieu of any compensatory time off otherwise due for the emergency duty so compensated.
The governing body of the municipality, if necessary, may make emergency appropriations to provide funds for the payment of such compensation as provided by law.
N.J.S. § 40A:14-50