Class 5
Class 5 — oxidizers and organic peroxides
Class 5.1 is oxidizers. Class 5.2 is organic peroxides. They feed a fire rather than behaving like ordinary freight.
Class 5 splits in two. Division 5.1 is oxidizing substances: materials that can make other materials burn more fiercely. Division 5.2 is organic peroxides, which can be thermally unstable in their own right.
An oxidizer placard is not a flammable-liquid placard. The car may not burn on its own the way gasoline does, and it can still make a fire much worse. That distinction is the whole point of giving it a separate class.
Read the division. A photograph that shows a 5 and hides the decimal is an incomplete note.
Identification only. If a car is leaking or in a wreck, move away and call your local emergency number. Responders use the Emergency Response Guidebook. This page is not that book.