Flammable liquid Upper explosive limits

The flammable properties of substances in air include their flash point, vapor pressure, autoignition temperatures, and flammability range (i.e., their lower and upper explosive limits). Liquids that have a flash point of <100°F (37.8°C) are termed flammable, whereas liquids that have a flash point of 100-200°F (37.8-93.3°C) are termed combustible. These terms are explained in detail... 

The flammability of a liquid (as vapor) or that of a gas falls between two fairly definite limits of concentrations of the vapor (or gas) in the air. These are the lower explosive limit (LEL) and the upper explosive limit (UEL). These concentration limits in air are also known as the lower and upper flammable limits. The LEL is the minimum concentration of the vapor (or gas) in air below which a flame is not propagated on contact with a source of ignition. There is also a maximum concentration of vapor... 

The third component of a fire is the vapour, which can mix with air, over the surface of a flammable liquid. Solvent vapours will only burn in air over a restricted concentration range bounded by the UEL (upper explosive limit) and LEL (lower explosive limit). Table 9.2 sets out for a typical range of flammable solvents their UEL and LEL values and their flash points, which are effectively the temperatures at which the solvent-saturated air attains the LEL. 

Limits of Flammability. Each flammable gas and liquid (as a vapor) has a limited range of flammable concentration in mixtures with air. The lower flammable limit (or lower explosive limit) is the minimum concentration below which a flame is not propagated when an ignition source is present such a mixture would be too lean to bum. The upper flammable limit (or upper explosive limit) is the maximum concentration of vapor in air above which a flame is not propagated — such a mixture is too rich. The flammable range (or explosive range) lies in between the two limits. 

The results for lower (LEL) and upper (UEL) explosive limits in air are presented in Table 3-1. The LEL and UEL values are the lower and upper concentrations (expressed as volume %) for flammability. The tabulation also provides the freezing and boiling point temperatures which are helpful in determining whether the substance is a gas, liquid or solid at ambient conditions. The tabulation is based on both experimental data and estimated values. 

Tetrahydrofuran is a flammable liquid with a flash point of 6°E and explosive limits ranging from 2% (lower) to 11.8 % (upper). It is incompatible with strong oxidizers and lithium-aluminum alloys. Peroxides may accumulate upon prolonged storage in the air. 

Flammability and Explosibility Nickel carbonyl is a highly flammable liquid (NFPA rating = 3) that may ignite spontaneously and explodes when heated above 60 °C. Its lower flammable limit in air is 2% by volume the upper limit has not been reported. Carbon dioxide, water, or dry chemical extinguishers should be used for nickel carbonyl fires. 

Dichlorobenzene (DCB, o-Dichlorobenzene, ODB, Orthodichlorobenzene), C(,H4Cl2, is a colorless to pale yellow liquid with a pleasant aromatic odor. It is a combustible liquid and can form explosive mixtures with air at or above 151"F. Combustion and thermal decomposition products include hydrogen chloride gas, phosgene and chloro-carbons. Its flammable (explosive) limits are as follows Lower 2.2%, Upper 9.2%. 

These tests cover the methods of determination of the minimum temperatme at which vapors in equilibrium with liquid solvent are sufficiently concentrated to form flammable mixtures with air at atmospheric pressure and eoneentration limits of chemicals. Flammable (explosive) limits are the percent levels, volume by volume, of a flammable vapor or gas mixed in air between which the propagation of a flame or an explosion will occur upon the presence of ignition. The leanest mixture at which this will occur is called the lower flammable limit. The richest mixture at whieh it will occur is the upper flammable limit. The percent of vapor mixture between the lower and upper limits is known as the flammable range. 

The flammable range, sometimes called the explosive range, of flammable gases and the vapors of flammable liquids is the numerical difference between their upper and lower explosive limits. Thus, the flammable range of gasoline vapor is 6.2 percent by volume. 

T. Urbanski, Influence of Non-Explosive liquids on the Detonation Rate of Solid Explosives , ArchProcesouSpalania 3 (2), 117—32 (1972) CA 78, 99944 (1973) [The author discusses the effect on the deton rate of adding w to PETN, RDX, p-Nitrotoluene or TNT in concns of from 5 to 40%. He reports that at low w concns the deton rate is minimized. As the w content increases the deton rate curve passes thru a maximum to reach a second minimum at the higher ( V 40%) level of w concn. The author concludes that the increase in deton rate can be attributed to three factors, the existence of a covolume, a phlegmatizing factor, and the result of mixing of two components, at least one of which is expl] 9) T.V. Ferris, Expansion of Methanol-Air Mixtures at Above Atmospheric Conditions , LossPrevn 8,15—19 (1974) CA 82, 45989 (1975) [Upper flammability limits were detd for various mixts of methanol with air, or a 30/70 02—N2 mixt with and without w. A rise of 12 vol % in the flammability limit above the nominal value of 36 vol % methanol in w-free air mixts is reported in the presence of liq w]... 

Because biphenyl is often transported in the molten state, a moderate fire hazard does exist under these circumstances. Biphenyl, with a flash point of 113°C, has a lower flammability limit of about 0.6% (by volume) at the flash point to an upper limit of 5.8% at 166°C (42). Dust explosions are a hazard when vapors from a hot liquid surface condense in air in a confined space. 

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