THE EFFECTS OF FIRE

A burning substance produces a number of chemical reactions. These reactions produce flames, heat, smoke, and number of gases and other combustion products. The gases and combustion products will reduce the amount of oxygen available for breathing. All of these effects are vitally important to you as a fire fighter. You must be prepared to protect yourself against them.

FLAME, HEAT, AND SMOKE

Personnel must be protected from the flames, heat, and smoke to avoid injuries or loss of life. Before you enter a compartment or area where there is a fire, you need to be dressed-out properly.

You will need to tuck your pants into your socks, button the collar on your shirt, and put on a helmet. Wear any other protective clothing prescribed by current directives. If you are a nozzleman or hoseman, you will also need to wear protective gloves and an oxygen breathing apparatus (OBA). The flames and heat from a fire can be intense. However, if you are dressed out properly and maintain adequate distance, you can minimize your chances of getting burned. The smoke will make it hard to see and breath. However, you can cope with these problems by wearing an OBA and a headlamp.

GASES

Some of the gases produced by a fire are toxic (poisonous). Other gases although nontoxic are dangerous in other ways. We will discuss briefly some of the more common gases that are associated with fires.

Carbon Monoxide

Carbon monoxide (CO) is produced by a fire when there is not enough oxygen present for the complete combustion of all of the carbon in the burning material. CO is a colorless, odorless, tasteless, and nonirritating gas. However, it can cause death even in small concentrations. A person who is exposed to a concentration of 1.28 percent CO in air will become unconscious after two or three breaths. They will probably die in 1 to 3 minutes if left in the area. CO also has a wide explosive range. If CO is mixed with air in the amount of 12.5 to 74 percent by volume, an open flame or even a spark will set off a violent explosion.

Carbon Dioxide

Carbon dioxide (CO2) is produced by a fire when there is complete combustion of all of the carbon in the burning material. CO2 is a colorless and odorless gas. Although CO2 is not poisonous, unconsciousness can result from prolonged exposure at 10 percent volume and higher. Above 11 percent volume, unconsciousness can occur in one minute or less. In a sufficient quantity, death could occur, since CO2 does not provide any oxygen to breathe. The danger of asphyxiation should not be taken lightly; CO2 does not give

any warning of its presence, even when it is present in dangerous amounts. It does not support combustion and it does not form explosive

mixtures with any substances. Because of these characteristics, CO2 is very useful as a fire extinguishing agent. It is also used for inerting fuel oil tanks, gasoline tanks, and similar spaces.

Hydrogen Sulfide

Hydrogen sulfide (H2S) is generated in some fires. It is also produced by the rotting of foods, cloth, leather, sewage, and other organic materials. H2S can be produced within 6 to 12 hours. Use caution when fighting fires around sewage systems and in spaces where there has been a sewage spill. H2S is a colorless gas that smells like rotten eggs. Air that contains 4.3 to 46 percent H2S is violently explosive in the presence of a flame. H2S is extremely poisonous if breathed, even in concentrations as low as 20 ppm. You may rapidly become unconscious, stop breathing, and possibly die after one breath in an atmosphere that contains 1,000 to 2,000 ppm of H2S.

Hydrogen Chloride

Hydrogen chloride (HCl) is emitted by fireretardant paper (Federal Specification UU-P-268) when the paper is exposed to temperatures of 200F (93C). Also, Flexifloor tile MT 202 (Butyl rubber MI L-M- 15562) exposed to temperatures of 400F (204C) will emit HCl. The level of HCl emitted is four times the authorized safe level of 5 ppm. Breathing concentrations of 1500 ppm is fatal in just a few minutes.

Hydrogen chloride is a colorless, nonflammable gas, which is soluble in water. The gas could be found in a mist form. It is corrosive to the eyes, skin, and mucous membranes. If you have a fire in a compartment where fire-retardant paper or tile is located, be sure to wear an OBA until the compartment is tested and found safe for personnel without an OBA.

Phosphine

Phosphine (PH3) is also emitted by fireretardant paper (Federal Specification UU-P-268) when the paper is exposed to temperatures of 200F (93C). Flexifloor tile MT 202, (Butyl rubber MIL-M-15562,) will also emit PH3 when exposed to temperatures of 400 "F (204 'C). The level of PH3 emitted is 23 times the authorized safe level of 0.3 ppm.

Phosphine is a colorless gas that has an odor of decaying fish. It is soluble in water and in organic solvents, and it ignites at a low

temperature. The odor of the gas may be nauseating. When PH3 is suspected, wear an OBA until atmospheric tests show that the area is safe.

INSUFFICIENT OXYGEN

A fire in a closed compartment may cause an inadequate supply of oxygen for breathing. An enormous amount of oxygen is used by the fire itself, leaving relatively little oxygen to breathe. The amount of oxygen normally present in the air is 20.8 percent. You breathe and work best with this amount of oxygen. When a space is suspected of having an insufficient amount of oxygen, wear an OBA. Keep the OBA on until atmospheric tests show that oxygen content is at least 20 percent and no more than 22 percent by volume.

FIRE EXTINGUISHMENT

In general, fires may be extinguished by removing one side of the fire triangle (fuel, heat, or oxygen) or by slowing down the rate of combustion. The method or methods used in any specific instance will depend upon the classification of the fire and the circumstances surrounding the fire.

THE REMOVAL OF FUEL

Although it is not usually possible to actually remove the fuel to extinguish a fire, there may be circumstances in which it is possible. If part of the fuel that is near or actually on fire can safely be jettisoned over the side, do so as soon as possible. Damage control parties must stand ready at all times to shift combustibles to safe areas. Take whatever measures possible to keep additional fuel away from the fire. In particular, immediately close supply valves in fuel oil, lube oil, and JP-5 lines.