Hazard Class 5 Oxidizers are separated into two divisions: 5.1 and 5.2. Class 5.1 materials are solids and liquids that, according to the DOT, “by yielding oxygen, can cause or enhance the combustion of other materials.” Although that is not a technical definition from a chemistry standpoint, it gets right to the point for emergency response purposes. While oxidizers themselves do not burn, if present in a fire situation, they will make the fire burn faster and become more difficult to extinguish.