Hazmat Placards Meanings 

Hazmat placards provide critical information about the kind of materials that are being transported and the risks associated with them. The hazardous chemicals/dangerous goods are divided by the United Nation Committee of Experts on the Transport of dangerous goods into a number of classes and colours, and it is crucial that anyone who handles or works around hazardous materials is able to identify their placards and what they mean. 

Hazmat Placard Classes And Colours Explained:

Numbers 1-9 represent the different hazardous classes and their divisions (class numbers are located at the bottom of the sign):  

• Class 1 – Explosives 
• Class 2 – Gasses
• Class 3 – Flammable and combustible liquids
• Class 4 – Flammable materials
• Class 5 – Oxidizer and organic peroxide
• Class 6  – Poisons
• Class 7 – Radioactive  
• Class 8 – Corrosive
• Class 9 – Miscellaneous

In addition to the class numbers, one of the easiest ways to identify hazard warning placards is by their color:

Blue Diamond

A Blue symbol represents goods that are dangerous when wet. This means that when these materials mix with water, they can become flammable. Examples include sodium, calcium and potassium. You’ll see dangerous when wet, an image of a flame and the number 4 on these placards. 

White And Black Diamond

Half white and half black signifies corrosive materials that can irritate and harm the skin. Examples include batteries, hydrochloric acid, sulfuric acid and sodium hydroxide.

White Diamond

A white diamond indicates poisonous and hazardous substances like dyes, acids, aerosols and medical waste.  For toxic materials, the sign will be labelled poison, PG III (PG = packing group) or inhalation hazard with a skull-and-crossbones image. For biohazards, the placard will say infectious substance and have a biohazard symbol (three circles overlapping one centre circle). 

Red Diamond

A red diamond represents flammable goods like gasoline, rubbing alcohol, paint and acetone, which can fall into Classes 2 or 3.

Green Diamond

Green indicates non flammable substances like compressed and liquefied gases.

Yellow Diamond

Yellow indicates oxidisers i.e. substances that, when mixed with oxygen, are likely to combust (Classes 2 or 5). Common oxidizers include ammonium nitrate, potassium nitrate, halogens and nitric acid.

Red And White Diamond 

If you see a sign that’s half red and half white with spontaneously combustible writing on it, a flame graphic and the number 4, that means there are substances present that may ignite when exposed to air. This can include things like aluminium and lithium alkyls or white phosphorus. 

Orange Diamond 

Orange represents explosive materials which can include products like dynamite, fireworks and ammunition. These signs typically have the words explosives or blasting agents on them and a graphic indicating something blowing up. They’ll also have the number 1 to indicate the class. 

Browse our extensive range of hazard warning diamond labels and signs here. To find out more, visit our website or contact us at 01686 611 377

Written by Kate Jones, for Morsafe Supplies.