The Action Point (AP) cost is unchanged. From page 4 of the rule book
A player gets 4 Action Points (AP) to spend on their turn. Each Action has a corresponding AP cost to perform. A player may select from any of the available Actions in any order and spend the appropriate AP to perform it. An action may be performed more than once per turn, so long as the AP cost is spent each time that Action is performed.
Players may pass. Unspent AP are saved from turn to turn. [...]
Extinguish – Use your gear to fight the fire in the Firefighter’s space or an Adjacent space:
- Remove a Smoke marker from the Board: 1 AP • Flip a Fire marker to Smoke: 1 AP
- Remove a Fire marker from the Board: 2 AP
It is usually best to completely Extinguish Fire (2 AP); Smoke is liable to reignite.
So, the CAFS Firefighter has to spend the normal 2 AP to fully extinguish fire, but they can use their free Extinguish AP that cannot be saved between turns.
CAFS Firefighter - 3 AP plus 3 free Extinguish AP per turn. Free Extinguish AP cannot be saved.