Combustion Flammability Ignition sources

The autoignition temperature is the minimum temperature required for self-sustained combustion in the absence of an external ignition source. The value depends on specified test conditions. Tht flammable (explosive) limits specify the range of concentration of the vapor in air (in percent by volume) for which a flame can propagate. Below the lower flammable limit, the gas mixture is too lean to burn above the flammable limit, the mixture is too rich. Additional compounds can be found in National Fire Protection Association, National Fire Protection Handbook, 14th ed., 1991. 

The ignition temperature or autoignition temperature is the minimum temperature of a flammable mixture that is required to initiate or cause self-sustained combustion without ignition from an external source of energy such as a spark or flame (ASTM D2155). 

Provide damper mechanical position stop to prevent complete closure of damper Eliminate ignition sources within the ductwork Use bonding and grounding Eliminate flammables or combustible by material substitution Use inert atmosphere... 

Fire Hazards - Flash Point Not pertinent Flammable Limits in Air (%) 1.6- 10 Fire Extinguishing Agents Stop flow of gas Fire Extinguishing Agents Not To Be Used Not pertinent Special Hazards of Combustion Products Not pertinent Behavior in Eire Containers may explode in fires. Vapor is heavier than air and may travel considerable distance to ignition source and flash back Ignition Temperature (deg. F) 725 Electrical Hazard Not pertinent Burning Rate No data. 

The methods described in this chapter are meant for practical application background information is given in Chapter 4. If a quantity of fuel is accidentally released, it will mix with air, and a flammable vapor cloud may result. If the flammable vapor meets an ignition source, it will be consumed by a combustion process which, under certain conditions, may develop explosive intensity and blast. 

Confined combustion explosions (gaseous or liquid) usually occur when a flammable vapor leaks into an enclosure and mixes witJi air to form a flarmnable mix-ture, whereupon this mix+ure contacts an ignition source tliat was present before the leak occurred. This type of explosion ctm tUso occur in storage taitks or sliips where tlie vapor space above tlie stored flanunable liquid (fuel) is in tlie cxplosivity range. In tliis case, an ignition source accidentally introduced will cause an explosion. 

When an ignition source is brought into contact with a flammable gas or mixture of gases, a combustion chemical reaction will occur at the point of introduction provided an oxidizer is present, normally oxygen. The combustion components are commonly referred to as a simple fire triangle ... 

Upper Explosive Limit Also known as Upper Flammable Limit. Is the highest concentration (expressed in percent of vapor or gas in the air by volume) of a substance that will burn or explode when an ignition source is present. Theoretically above this limit the mixture is said to be too rich to support combustion. The difference between the LEL and the UEL constitutes the flammable range or explosive range of a substance. That is, if the LEL is one ppm and the UEL is five ppm, then the explosive range of the chemical is one ppm to Five ppm. (See also LEL)... 

Examples Aluminum alkyl Grignard reagent Finely divided metals Iron sulfide Examples Noncombustible materials Flammables or combustibles needing an ignition source to start burning... 

A fundamental element of fire prevention is the control of ignition sources. The process should be designed, installed, and operated to minimize or prevent the release or spill of flammable gases, liquids, or combustible dusts, as well as eliminate or control ignition sources. The basic controls for these unwanted ignition sources are ... 

Fire prevention efforts for handling flammables and combustibles rely heavily on the mechanical integrity of the transfer system, the containment of small spills that do occur, and the control of ignition sources. While operator presence in the immediate area of the rack or wharf is recommended for any loading or unloading operation, full-time surveillance at the unloading spot is recommended. 

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