Industrial gases in the national standard "common dangerous chemicals Classification and signs" (gb13690-1992), is usually classified as the 2nd category of compressed gas and liquefied gases. This type of chemical refers to a compressed, liquefied or pressurized dissolved gas. When the gas is pressurized or lowered, the distance between the molecules of the gas can be greatly reduced and pressed into the cylinder, which is called a compressed gas (also known as a permanent gas, such as oxygen, nitrogen, argon, hydrogen, etc.). Continue to pressure compressed gas, appropriate cooling, compressed gas will become liquid, known as liquefied gases (such as liquid chlorine, liquid ammonia, liquid carbon dioxide, etc.). In addition, there is a very unstable nature of the gas, pressurized after the need to dissolve in the solvent stored in the cylinder, the gas is called dissolved gas (such as dissolved acetylene, etc.).
Industrial gases according to their chemical properties, can be divided into 4 categories: ⑴ highly toxic gases, with extremely strong toxicity, invasive human body can cause poisoning and even death. such as chlorine, ammonia and so on. ⑵ flammable gas has the advantages of easy combustion and chemical explosion, and has certain toxicity. such as hydrogen, acetylene and so on. ⑶ helps the gas body, has the combustion-supporting ability, but does not burn itself, exists the danger which expands the fire, like oxygen and so on. ⑷ not gas, the person is suffocating, stable nature, not burning, such as nitrogen, carbon dioxide and argon. National standard gb13690-1992, the above 4 kinds of gases are divided into 3 small categories, namely, Category 2.1 flammable gases, 2.2 types of non-gas bodies (including fuel gas), class 2.3 Toxic gases.