Understanding DOT Class 5 Materials: Oxidizers and Organic Peroxides


DOT Class 5 materials

Definition of DOT Class 5: Oxidizer and Organic Peroxide Materials

Class 5 covers oxidizers and organic peroxides.

The formal definition for 5.1 oxidizers can be found at 49 CFR 173.127 and the formal definition for 5.2 organic peroxides can be found at 49 CFR 173.128.

Class 5 Divisions

Class 5 materials are grouped into two divisions.

Division 5.1

Division 5.1 materials are oxidizers, meaning materials that can increase the potency of a fire. This mechanism is typically associated with the release of oxygen by decomposition.

Division 5.2

Division 5.2 materials are organic peroxides, containing the bivalent -O-O- structure. These materials are further subdivided into 7 types (A-G) depending on if they can detonate, deflagrate, and/or undergo a thermal explosion.

Relationship Between Class 5 and OSHA Hazard Classifications

Division 5.1 materials overlap with the OSHA Physical Hazard classifications of Oxidizing Liquids and Oxidizing Solids depending on their physical state.

Division 5.2 materials use the same oxygen content (%) calculation formula as the OSHA Physical Hazard Organic Peroxide classification criteria. The OSHA classification also uses the same 7 types (A-G) for subclassification.

where, for a material containing a number of species of organic peroxides:

n = number of -O-O- groups per molecule of the species

c = concentration (mass percent) of the species

m = molecular mass of the species


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