Which fixed fire extinguishing system is primarily used to protect against fires involving flammable gases or liquids and electrical equipment?

• A. Carbon dioxide
• B. Halon
• C. Water mist
• D. Wet chemical

Answer: (A)

Carbon dioxide fixed extinguishing systems are designed for spaces housing electrical equipment and fuels (flammable liquids or gases). They extinguish by rapidly displacing the air (lowering the oxygen level) in an enclosed space, which quickly suppresses the flame without leaving residue that could damage sensitive equipment. Because occupants would be at risk from the oxygen drop, these systems are installed in unoccupied or controlled-occupancy areas, making them well suited for protecting electrical gear and areas where flammable fuels could ignite.

Halon systems have strong suppressive capability for electrical and liquid/gas fires but are being phased out due to environmental concerns, so modern practice relies more on other clean agents or water-based options. Water mist can handle many A/B/C fires and is safer for occupied spaces, but it involves introducing water and isn’t as specifically tailored to protecting enclosed electrical rooms. Wet chemical is targeted for commercial kitchens and isn’t applicable to protecting general electrical equipment or hydrocarbon gas/liquid fires.