How do submarines fight fires near their batteries?

If sea water on submarine batteries can produce chlorine gas, what do submarines use to fight fires?

Foam and other dedicated fire-extinguishing systems, selected to avoid creating an additional battery-related hazard.

Seawater used against a fire can create a chlorine hazard if it reaches a submarine's batteries. Foam and other extinguishing systems provide alternatives. The choice must account for secondary chemical hazards as well as the original fire.