Fire safety requires specialized knowledge, particularly when dealing with electrical fires. These incidents, known as Class C fires, involve energized electrical equipment, introducing the severe risk of electrocution alongside the physical danger of the flames. Knowing the correct, safe procedure is essential for successfully containing a small fire and preventing a catastrophic safety event. Understanding how to address a Class C fire ensures personal safety and minimizes property damage that results from using the wrong extinguishing method.
Identifying Class C Fires and Immediate Safety Steps
A Class C fire involves energized electrical equipment, meaning the apparatus is still connected to a power source and conducting electricity. This classification applies to fires fueled by wiring, outlets, appliances, or any device where an electrical current is present. The unique danger is the risk of electrical shock or electrocution posed by the live current, not the burning material itself. Applying any conductive agent will energize the extinguishing medium, creating a path for the current to travel directly to the person fighting the fire.
The first priority when confronted with a Class C fire is to de-energize the equipment if it can be done safely. This involves unplugging the specific device, turning off the dedicated circuit breaker, or throwing the main power switch. Removing the electrical current eliminates the Class C hazard, converting the incident into a more manageable Class A fire involving ordinary combustibles. If the power source cannot be immediately and safely cut off, the fire must be treated as a live electrical hazard, requiring specialized non-conductive extinguishing agents.
The Dangers of Using Water-Based Extinguishers
Standard fire extinguishers containing water or foam are dangerous and ineffective when used on an energized electrical fire. Water is a highly efficient conductor of electricity due to dissolved ions and impurities. Spraying a stream of water onto a live electrical fire creates a conductive path that allows the current to travel from the energized equipment, through the water stream, and back to the operator. This action instantly creates a risk of electrical shock, which can be fatal.
Water-based agents are incapable of counteracting the continuous source of ignition provided by the electrical current. Even if the water stream momentarily cools the burning material, the live electricity will continue to arc and reignite the fire. Using water can also cause the fire to spread as the energized water runs along surfaces, expanding the area of electrical hazard and damage. These methods are incompatible with Class C fire safety due to the risk of electrocution and failure to suppress the heat source.
Choosing the Right Extinguishing Agent
The National Fire Protection Association (NFPA) standard specifies that any agent used on a Class C fire must be electrically non-conductive. This non-conductivity is designated by the “C” rating on the extinguisher label, confirming its safety for use on energized equipment. Three primary types of agents meet this requirement: dry chemical, carbon dioxide (CO2), and clean agents. Each agent works differently to suppress the flames without creating an electrical hazard.
Multi-purpose dry chemical extinguishers, often labeled ABC, contain monoammonium phosphate and work by interrupting the chemical reaction of the fire and creating a barrier between the fuel and oxygen. While highly effective and widely available, the fine powder leaves a corrosive residue that can severely damage sensitive electronic equipment, requiring extensive cleanup.
Carbon dioxide (CO2) extinguishers are clean and work by displacing oxygen, effectively smothering the fire. However, CO2 is discharged as a cold gas/snow cloud with a short effective range, typically three to eight feet. It can cause thermal shock to components and frostbite if the operator touches the discharge horn.
Clean agents, which are modern alternatives to the phased-out Halon, are the optimal choice for areas with sensitive electronics like server rooms. These agents, often halocarbons, are electrically non-conductive and extinguish the fire as a gas or mist, leaving no residue. Though generally more expensive, they minimize collateral damage, making them the preferred option for protecting high-value assets. Selecting the appropriate agent depends on balancing fire suppression effectiveness with the potential for equipment damage and the specific environment.
Executing the Extinguishing Procedure (P.A.S.S.)
Once the correct, non-conductive extinguisher is selected and the fire is confirmed to be small and contained, the P.A.S.S. method provides the tactical procedure for safe operation. The first step is to Pull the safety pin, which breaks the tamper seal and allows the handle to be depressed. The operator must then Aim the nozzle or horn low at the base of the fire, where the fuel source is located, rather than at the visible flames.
The operator must Squeeze the handle slowly and evenly to discharge the extinguishing agent. Maintain a safe distance of approximately six to eight feet from the fire while discharging the agent, moving cautiously closer only as the fire begins to diminish. The final step is to Sweep the stream from side to side across the base of the fire, continuing until the flames are completely extinguished.
It is crucial to watch the area for a few moments after extinguishing, as the fire can easily re-ignite if the electrical source was not cut or the heat was not fully suppressed. If the fire spreads rapidly, the extinguisher is depleted, or the safe exit is blocked, abandon the attempt immediately and evacuate. The fire department should be contacted afterward to verify that the power is secured and to check for hidden electrical damage.