explosives
COLOR
It indicates a flammable or explosive gas.
The Dangerous When Wet placard is a square on point (or diamond) placard with white markings on a blue background. The words "Dangerous When Wet are printed across the middle, with a drawing of a flame centered in the upper corner, and the numeral four (4) in the bottom corner to indicate the Hazard Class.
The hazard class of the substance being carried
symbol, UN hazard class number, color, UN identification number
A placard identifying hazard class 6 describes the presence of a poisonous gas. For an image, see the related link, below.
Poisonous or infectious materials are in Hazard Class 6. The several labels and placards for Class 6 are white in color, with black printing.
The placard on a tanker carrying hazardous materials will tell you the class of the hazard (flammable, explosive, corrosive, etc). If you have access to the North American Guide or a similar reference, the placard will also tell you something a bit more specific about the identity of the hazardous material - its category, or sometimes its chemical name.
It is to designate Class 1 - Explosives (dynamite, black powder).
Hazard Class 3
Class 1 materials are explosives.Materials that have an explosive hazard are in Hazard Class 1.
DOT class 8 are corrosive.