All chemicals are divided into combustible, non-flammable and non-flammable according to their degree of flammability.
Combustible substances are divided into highly flammable and highly flammable. Most organic solvents, except for a number of halogen-containing solvents, belong to LZR – flammable liquids, which are divided into three categories.
1 grade
Flammable substances are especially dangerous. The flash point of solvents of this grade is from 18 °C and lower, in a closed crucible, or below 13 °C in an open crucible. Typical representatives of flammable substances are isopentane, hexane, cyclohexane, gasoline, petroleum ether, diethyl ether, acetone, tetrahydrofuran. The main feature of such solvents is high saturated vapor pressure at normal temperature. For this reason, the vapors of these liquids in case of poor tightness of the vessels can very easily spread in the air at a great distance from the place of storage and instantly ignite.
2nd grade
The second category includes permanently dangerous LZR with a flash point in the range from -17 to + 23 ° C in a closed crucible or in an open crucible from -12 to + 27 ° C. A distinctive feature of such liquids is the ability of their vapors to form a flammable mixture with air at normal temperature. Also, under these conditions, an explosive environment is formed in the vapor-air phase of a closed vessel. Therefore, LZR of the 2nd category are much more dangerous than LZR of the 1st, because the latter in closed vessels at normal temperature form a vapor concentration that is above the ignition limit. Class 2 flammable solvents include isooctane, naphtha, toluene, diethyl ketone, methyl ethyl ketone, ethyl and methyl acetate, lower alcohols.
3rd grade
The third category includes flammable liquids at high temperatures. Their flash point is in the range of 23-61 °C in a closed crucible or 27-66 °C in an open crucible. The concentration at which the vapors of these solvents can work in the air is formed exclusively at an elevated temperature. At normal temperature, these LZR ignite only in the presence of an ignition source. Class 3 flammable substances include butyl acetate, xylene, turpentine, white spirit, solvent, amyl acetate, cyclohexanone.