I would think it depends upon the dept as opposed to a state mandate. I can't really see where a volunteer dept is subject to a cutoff age just like say the LAFD. In most cases, a cutoff age is something that a career dept imposes and in such cases, the age limit has nothing to do with ability to do the job, but instead, to ensure enough time in the job prior to retirement age.
Thanks I know back home in Indiana the cut off for a paid dept is 35. I was thinking about getting on out here in California and was wondering if it was the same.
Best bet would be to look up individual depts in regards to their requirements. A simple search on a dept tends to have an employment page where applicant requirements are noted. Just my guess is there probably is no max age set by the state. Doing a quick search of San Francisco, Los Angelas, and San Diego, the minimum age to apply is 18, but there is no max age.