To begin to plan for a more fire safe structure and live with the enemy “fire” in terms of prevention and escape one must first understand the basic elements of fire growth.
IGNITION: Almost all fires start from a small flame source; even explosions generally are caused by a spark or other small flame. Ignition has occurred when a fire is able to sustain itself for any period of time. Statistics indicate that the vast majority of all fires are generated from the uncontrolled rise in temperature of a small heat source. At the early stage of a fire. The ignition phase, is most critical, for once ignition has occurred, the fire will be able to continue its growth only if it can feed on nearby flammable materials. By raising the temperature at which a material will ignite or support combustion, you have effectively reduced the material’s flammability. Natural fiber materials treated with Nochar’s fire retardant have a much higher ignition or combustion temperature. For example, wood normally combusts at 523 degrees Fahrenheit. However when treated with “NFP”, the combustion temperature has been raised to well over 1,000 degrees Fahrenheit (There is a direct correlation between surface and mass. Two pounds of thinly sliced wood veneer has a much lower combustion temperature and faster flame spread rate than the same wood in a 2 pound block. The more mass there is the more temperature is diffused throughout the wood, thus naturally slowing down the phenomenon of ignition.) The actual combustion or ignition temperature of materials treated with “NFP” depends on the amount of solids absorbed by the treated material. For example, wood treated with a surface spray or dampening will have a lower ignition temperature than wood treated by a vacuum process, pressure treatment or other newly developed methods. This is demonstrated by the flame spread rating difference in an E-84 Tunnel Test. Class A vs. Class C.
RADIATION: Once ignition has taken place in a material, it begins to produce heat energy on its own, or BTU output, which is radiated in all directions. The radiated heat of energy begins to raise the temperature of everything around the original flame.
• Radiation or heat flux is the focal point of much fire research being conducted today. Each type of material used produces a different amount of radiant heat or rate of heat flux. For example, normally speaking, synthetic material will produce twice the amount of radiant heat as a natural fiber. By calculating the amount of heat flux or watts of energy generated by various materials in a room, called the fuel load, adequate sprinkler systems can be designed producing the needed amount and flow rate of suppression liquids. The speed and direction of the fire growth can also be predicted.
Radiant heat given off by burning material heats the air around the flames causing the air to rise toward the ceiling of the room taking with it any byproducts of incomplete combustion, such as smoke and gasses. Heat, smoke and gasses begin to build from the ceiling down within seconds of the first flicker of flame in a typically furnished room.
FLAME SPREAD: Flame spread occurs as a result of the temperatures of materials surrounding the initial ignition flame, reaching combustion level as a result of radiated heat. The speed of this phenomenon increases in direct relationship to the size of the flame and the amount of surface involved in combustion. The larger the flame, the greater the amount of heat radiated and the faster the flame spread. Natural fiber materials treated with a Nochar fire retardant and tested in the E-84 Tunnel Test indicates a drastic reduction in flame spread through the control of radiant heat. For Example, a 5\8″, spruce-faced plywood has a normal flame spread of between (140) and (170). When treated with “NFP” in a spray-on treatment, the flame spread is reduced to below (75), or 50% going from a Class C to a Class B. The same plywood treated by either vacuum or other newly developed methods has a flame spread value of less than (25) or a Class A.
CONVECTION: The spiraling or circulatory movement of air. The heated air caused by radiation starts the heated air rising toward the ceiling where it is deflected by air current constantly rising from the heat source. As the heated air travels across the room it begins to cool down and sink toward the floor as more heated air is pushed upward, always carrying with it the hydrocarbons and by-products of the incomplete combustion (smoke). As the volume of moving air increases and builds speed the temperature begins to rise even faster. A soft yellow flame has a temperature of approximately 560 degrees Fahrenheit: however, when this flame is fanned by air current, the temperature begins to take a quantum leap and will almost instantly reach 1,600 degrees to 1,800 degrees Fahrenheit in a room.
FLASHOVER: Flashover occurs when the temperature is sufficient to cause all of the available combustible surfaces and the by-products of incomplete combustion to ignite spontaneously and simultaneously. When the heat and the expansion of gases become more than the room can contain, flashover occurs. Flashover usually causes windows to shatter and doors to he blown off their hinges. Nothing survives flashover.
Flashover occurs in approximately two minutes after the first flicker of flames. Flashover occurs as a result of decorative materials and furnishings acting as a fuel load and accelerant. Rarely does flashover involve structural assemblies until the resultant heat and combustion caused by flashover consume the membrane of a wall sufficiently to penetrate a wall cavity or penetrate the roof support plenum.
