From the 2008 rulebook, updated fire paragraph:
3.Q FIRE EXTINGUISHING SYSTEMS:
All cars and enclosed motorcycles shall have a minimum of one driver-controlled fire extinguishing system using a minimum of 5 lbs. of extinguishing agent designed and applied to function as driver protection.
Approved agents include Halon 1301, Halon 1211, DuPont FE36, and certain AFFF systems including Cold Fire 302, ESS Foam, Firefox Gem Foam or other Halon replacement certified by the manufacturer for use in a confined space. Dry chemical and CO2 may be used in the engine compartment only. The application and installation shall be in accord with the manufacturer’s recommendations and consistent with the size and shape of the driver’s compartment. The discharge rate should be designed to allow sufficient protection for the time it will take the car to stop from speed.
DW