Substances that need extremely high temperatures to burn are
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Last Updated: December 9, 2020 4:07:43 PM PST See storage requirements for flammable and combustible liquids in UC San Diego facilities. Flammable and combustible liquids present a danger of personal injury and property damage, so strict storage requirements are both essential and required by law. Because their vapors ignite and burn easily, flammable and combustible liquids have strict storage requirements. The hazard classification of a liquid determines the type and size of container in which it can be stored. For more information, see: National Fire Protection Association (NFPA) hazard classifications for flammable and combustible liquids are listed below: Last update 01/08/2022 What causes an explosion is the combustion of gas. For this to occur, 3 elements are needed: - Combustible: the gas - Oxidizer: the air (oxygen) - Ignition: can be of various kinds The concentration of fuel and oxidiser influences whether combustion can take place or not. A range of fuel-combustion concentration is established within which combustion is possible. The lower and upper limits of this range are called the Lower Explosive Limit (LEL) and an Upper Explosive Limit (UEL) respectively. Below the LEL the fuel concentration in the mixture is not sufficient to allow the reaction to take place, above the UEL the fuel concentration is very high at the expense of a reduced oxidiser concentration, in which case too the reaction cannot take place. Depending on the volumetric concentration of the air, the necessary energy that the ignition must supply in order to have combustion varies, we speak in this case of Ignition Energy and it depends on the fuel considered. Below is a graph showing the ignition energy required for propane and hydrogen as the air concentration varies. Autoignition temperature and flash pointTwo temperatures are defined which characterise flammable substances: - Flammability temperature or Flash Point: this is the lowest temperature at which vapours are formed in such quantities that in the presence of oxygen (air) and an ignition source they give rise to the phenomenon of combustion (the gas becomes flammable and can therefore explode). - Autoignition temperature: the lowest temperature at which the substance begins to burn spontaneously in the presence of oxygen, without an external source of ignition. Every substance has its own flash point and self-ignition temperature. On the basis of the flammability temperature, the various flammable liquids are classified: - Category A (Ti<21°C): petrol, alcohols; these are the most dangerous products as they are extremely flammable even at room temperature and must be kept away from possible ignitions; - Category B (21 °C ≤ Ti ≤ 65 °C): diesel fuel; - Category C (Ti > 65 °C): glycerine, bitumen. Category A and B flammable liquids are in turn divided into (Classification of flammable substances according to Directive 67/548/EEC): - R10 Flammable: Liquid substances and preparations having a flash point t > 21°C and < 55°C. - R11 highly flammable: Liquid substances and preparations having a flash point t > 0 °C and < 21 °C. - R12 extremely flammable: Liquid substances and preparations having a flash point T < 0 °C. The Auto-ignition temperature determines the Temperature Class to which a Gas belongs. Table 5.5-A shows the Classes associated with the auto-ignition temperature values. The temperature classThe Auto-ignition temperature determines the Temperature Class to which a Gas belongs. Table 5.5-A shows the Classes associated with the auto-ignition temperature values. Gas groupBased on their hazardousness, related to the places where they are typically present or the minimum ignition energy, the gases are also divided into groups: - Group I: Grisou - Mine gas (~80% Methane). M.I.E.=0.28mJ - Group IIA: Propane, Gasoline, Methanol. M.I.E.=0.16mJ - Group IIB: Ethylene. M.I.E.=0.06mJ - Group IIC: Hydrogen, Acetylene. M.I.E.=0.02mJ The gas is then identified by Temperature Class and Group. This information is shown on the CE marking of products used in a particular ATEX Zone. What are highly flammable substances?Flammable: A liquid with a flash point under 100°F is considered flammable. Examples: gasoline, acetone, toluene, diethyl ether, alcohols.
What causes burning flammable substances?Any combustible substance will burn if it's subjected to enough heat. The lowest temperature at which a flammable or combustible liquid will ignite — and continue to combust without the presence of a spark or flame — is defined as the auto-ignition temperature.
What gas is highly flammable?Chlorine trifluoride is the most flammable gas
It's deceptively colourless, extremely reactive, and capable of burning through concrete and gravel. Perhaps the most concerning fact about this gas though is that it can burn without any ignition source, therefore exceeding the oxidising power of even oxygen itself.
What materials can burn?All fabrics will burn, but some are more combustible than others. Untreated natural fibers such as cotton, linen and silk burn more readily than wool, which is more difficult to ignite and burns with a low flame velocity.
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