Reactivity hazard rating is based on the potential of the material to release energy either by itself of when in contact with water. Flammability hazard rating: (4) the preferred fire attack is to stop the flow of material (3) materials that can be ignited under almost all normal temperature conditions (2) materials must be moderately heated before ignition will occur (1) materials that must be preheated before ignition will occur (0) material will not burn. (0) materials offer no hazard beyond that of ordinary combustible material. Health hazard ratings mean the following: (4) materials could cause death (3) materials could cause serious temporary or residual injury (2) materials could cause temporary incapacitation (1) materials could cause irritation, but minor residual injury. (5) means alcohol-resistant fire fighting foam is recommended. (4) means water may be ineffective, except as a blanket. (3) means water may be used to blanket fire. (2) means water or foam may cause frothing. Extinguishing methods are listed by number. The vapor density of a substance is the ratio of the weight of a volume of pure vapor or gas to an equal volume of dry air at the same temperature and pressure. Specific gravity is the ratio of weight of that substance to the weight of an equal volume to another substance, in this case water. These boundary mixtures are known as lower and upper flammable or explosive limits. Similarly there is a maximum concentration above which propagation of flame does not occur. In gases, there is a minimum concentration of the material below which propagation of flame does not occur. The ignition temperature of a substance, whether solid, liquid, or gas, is the minimum temperature required to cause self-sustained combustion independently of the heating or heated element. The flash point of a liquid is the minimum temperature at which the liquid gives off sufficient vapor to form an ignitable mixture with air near the surface of the liquid. No single fire hazard property, such as flash point or ignition temperature, should be used to describe or appraise the fire hazard or fire risk of a material, product, assembly, or system under actual fire conditions. They are: flash point, ignition temperature, flammable limits, specific gravity, vapor density, boiling point, water solubility, extinguishing methods, and hazard identification. The substances listed have several categories listed to describe their fire hazard properties.
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