The degree of hazard of oxidizing agents may be evaluated by consideration of the National Fire Protection Association (NFPA) classification for oxidizers. NFPA identifies four classes of oxidizers with Class 1 nominally the least hazardous and Class 4 the most hazardous. The four classes of oxidizers are as follows:
Class 1 oxidizer: An oxidizing material whose primary hazard is that it may increase the burning rate of combustible material with which it comes in contact.
Class 2 oxidizer: An oxidizing material that will moderately increase the burning rate or that may cause spontaneous ignition of combustible material with which it comes in contact.
Class 3 oxidizer: An oxidizing material that will cause a severe increase in the burning rate of combustible material with which it comes in contact or that will undergo vigorous self-sustained decomposition when catalyzed or exposed to heat.
Class 4 oxidizer: An oxidizing material that can undergo an explosive reaction when catalyzed or exposed to heat, shock, or friction.
Thus, the relative degree of hazard decreases in the following order for oxidizers: 4 {>} 3 {>} 2 {>} 1. The following table illustrates examples of oxidizers in each NFPA class.
Some typical oxidizers by NFPA classification.[Note a]
a. NFPA 43A-1980, Code for the Storage of Liquid and Solid
Oxidizing Materials.
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