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Oxidizing materials are liquids or solids that readily give off oxygen or other oxidizing substances (such as bromine, chlorine, or fluorine). They also include materials that react chemically to oxidize combustible (burnable) materials; this means that oxygen combines chemically with the other material in a way that increases the chance of a fire or explosion. This reaction may be spontaneous at either room temperature or may occur under slight heating. Oxidizing liquids and solids can be severe fire and explosion hazards.
Common oxidizing liquids and solids include:
There are other chemicals that are oxidizing materials. For example, liquid air has been involved in many explosions because of its oxidizing properties. Liquid air itself has about 30% oxygen which makes it a powerful oxidant. However, when liquid air evaporates, it becomes richer in oxygen content when more volatile components evaporate slightly faster. Liquid nitrogen is safer and is preferred to liquid oxygen as a cryogenic liquid coolant.
It is wise to treat any unknown material, especially crystals in solvents known to form a peroxide (e.g., ethers), as very hazardous until it is positively identified.
Oxidizing materials can:
What happens when an oxidizing material comes in contact with a combustible substance largely depends on the chemical stability of the oxidizing material. The less stable an oxidizing material is, the greater the chance that it will react in a dangerous way.
The [U.S.] National Fire Protection Association (NFPA) Code 430 (1995) "Code for the Storage of Liquid and Solid Oxidizers" has classified oxidizing materials classified according to their ability to cause spontaneous combustion and how much they can increase the burning rate.
The National Fire Protection Association (NFPA) Code 430 (1995) "Code for the Storage of Liquid and Solid Oxidizers" provides many examples of typical oxidizing materials listed according to the NFPA classification system. Some of these examples include:
Examples of NFPA Class 1 oxidizers include:
Examples of NFPA Class 2 oxidizers include:
Examples of NFPA Class 3 oxidizers include:
Examples of NFPA Class 4 oxidizers include:
Burning involves the oxidation of a combustible (burnable) substance. When a combustible substance burns, a chemical reaction occurs in which the substance (fuel) combines with oxygen, and gives off heat, gases, and often light (flames). The usual source of oxygen for burning is air. However, oxidizing materials can supply combustible substances with oxygen and support a fire even when air is not present.
Although most oxidizing materials do not burn themselves, they can produce very flammable or explosive mixtures when combined with combustible materials like:
Some oxidizing materials are also incompatible with non-combustible materials. These oxidizers can undergo dangerous reactions with water, inorganic acids or even other oxidizing materials.
The MSDS for a particular oxidizing material should explain what other substances the oxidizer is incompatible with (reacts in a dangerous fashion) and any other conditions, such as heat, shock or friction, that could result in dangerous chemical reactions.
Oxidizing materials may be toxic or corrosive. Depending on the material, route of exposure (inhalation, eye or skin contact, or swallowing) and dose, they could harm the body. Corrosive oxidizers can also attack and destroy metal.
The MSDSs and the container labels should explain all of the hazards of the oxidizing materials that you use in the workplace.
An example is ammonium perchlorate. This material is a white or colourless, odourless crystals. It is used in explosives and fireworks; as an oxidizing agent in solid rocket and missile propellants; as an adhesive; as an engraving agent; laboratory (analytical) reagent; chemical intermediate for alkali and alkaline metal perchlorates; animal feed supplement; and in oxygen-generating devices for life-support systems in submarines, spacecraft, bomb shelters and breathing apparatus.
Ammonium perchlorate can decompose at high temperatures forming toxic gases, such as chlorine, hydrogen chloride and nitrogen oxides. Closed containers or tanks may rupture and explode if heated. It does not burn but is a powerful oxidizer and explosive when mixed with combustible materials. It is highly reactive and impact or high temperatures can cause violent decomposition or explosion. It can form shock-sensitive mixtures with finely powdered metals, metal oxides, strong reducing agents, sulfur and phosphorus. It may cause eye irritation.
CCOHS also has some 50 databases containing different kinds of information. Some are bibliographic databases (e.g., NIOSHTIC, CIS-ILO, HSELINE, Toxline) which provide abstracts from journal articles, books, government reports, etc. There are other databases that have direct, ready-to-use information (e.g., CHEMINFO, HSDB, RIPP, etc). To find out about these databases and which ones have information on chemicals of interest to you, search the CHEMINDEX Database. When you search using a chemical name or synonym or Chemical Abstracts Service Registry Number (CAS RN), the search results list the databases that contain information on the chemical. The search results will also allow you to link to a description of the databases and view sample records.