Engine Fire Protection Systems Which statement best describes the blowout type indicator disk on a fixed fire extinguishing system? a. When the red indicator disk is missing, it indicates the fire extinguishing system is charged and ready for use. b. When the yellow indicator disk is missing, it indicates the fire extinguishing system has been normally discharged. c. When the green indicator disk is missing, it indicates that the fire extinguishing system may have been normally discharged.