Career and volunteer firefighters are both common

 The Mercury News has the story:

 

Where did all the Bay Area volunteer firefighters go?
Civilian volunteer firefighters used to be a staple of fire stations across Northern California. Today, few remain.  By Chase Hunter 

"Nationally, about seven in 10 fire personnel are volunteers, according to the National Fire Department Registry. These volunteers are largely confined to Midwest and East Coast states, Mokhtarian said, where fire risk poses a significantly lower threat and communities are not as flush with tax dollars as in the Bay Area."

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The career firefighters referred to above are local government employees.  As noted earlier in connection with the fires in Los Angeles, there are also private fire fighting services:

Monday, January 13, 2025  Are private firefighters repugnant (in Los Angeles)?