Initial Fire-Fighting Operations In fire-fighting operations, you must first determine the location and type of fire and then determine the method of extinguishing the fire, as shown in table 7-4. For complicated or simultaneous fires, fog will serve in nearly every situation. In case of a class C fire, first de-energize all circuits where possible. Next, establish fire boundaries by cIosing all doors, hatches, man- holes, ventilation ducts, and other vents in the area as practical and de-energize power as necessary. CO₂ Safety Precautions You must be aware that the very qualities that make  carbon  dioxide  (CO₂) a valuable ex- tinguishing agent also make it dangerous to life. When CO₂ replaces oxygen in the air where combustion cannot be sustained, there is no respiration. Prolonged exposure to carbon dioxide causes suffocation, very much as immersion in water does when a person drowns. CO₂ cannot be seen or smelled. It gives no evidence of its presence that can be recognized by the senses. Since CO₂ is heavier than air, it remains close to the surface of the space in a deep or shallow pool, depending on the amount of area covered and the amount of CO₂ used. When a portable carbon dioxide extinguisher is used, there is practically no breathing danger in the average compartment because its 135 cubic feet of CO₂ lies in a shallow pool well below the usual breathing level. When entering a compartment that contains carbon dioxide (or any other harmful gas) in a dangerous concentration, you must wear an OBA. Except in an emergency, you should not open a CO₂ flooded compartment for at least 15 minutes after it has been flooded. This delay is a precautionary measure to give all the burning substances time to cool down below their ignition temperature; this prevents reignition upon contact with air. Warn anyone who uses a carbon dioxide ex- tinguisher that the “snow” will blister the skin and cause painful burns if it is allowed to remain on the skin. Discharge of CO₂ leads to a buildup of a static electrical charge. You should keep the cylinder in contact (grounded) with the metal structure of the ship when discharging CO₂. Halon 1301 Hazards The mechanism by which Halon 1301 ex- tinguishes a fire is not thoroughly understood. The phenomenon appears to be a physical/chemical action that inhibits combustion. Halon 1301 has the ability to extinguish both the flammable liquid spill and spray types of fire. Halon 1301 decomposes upon contact with flames or hot surfaces above 900°F (482°C). While this decom- position allows the Halon 1301 to function effectively, it also results in the formation of several decomposition products, primarily hydrogen fluoride and hydrogen bromide. Fuel decomposition products, carbon monoxide, oxygen depletion, heat, and smoke create person- nel hazards. Personnel should not remain in a space where Halon 1301 has been released to extinguish a fire unless OBAs are worn. Although personnel can be exposed to concentrations of 5 to 7 percent of Halon 1301 for up to 10 minutes without danger to health, spaces should still be evacuated upon accidental discharge. If Halon 1301 is discharged where no fire exists, several hazards may arise. For example, noise from the discharge can be startling; turbulence may be sufficient to move light objects; direct contact with the vaporizing liquid may have a strong chilling effect and can cause frostbite and burns to the skin; and obscured vision may result because of condensation of water vapor in the air. If you are in a space where Halon 1301 is dis- charged and vision is obscured, do not move about until vision improves. Moving blindly could result in injuries. Preventing Spreading of Fires In fighting a fire, you should secure any breaches in bulkheads adjacent to the fire. Also, be sure to cool adjacent bulkheads. Remove any combustibles from nearby compartments or render the compartments safe by one or more of the following methods: Cool or smother compartments with fog. Fill compartments with CO₂. Flood compartments as practical. Postfire Action Start postfire action while fire fighting is still in progress. As the on-scene leader you should 7-12