i-Hazard is a fast offline tool that will help you decode the orange plates which are found in vehicles containing hazardous materials. You just need to fill in the orange fields with the corresponding codes you see on a plate.
The upper field is for either the Hazchem Code or the Kemler Code. The lower field is used for the Un Number, which is typically a numerical value.
Sources
https://en.m.wikipedia.org/wiki/UN_number
https://en.m.wikipedia.org/wiki/Hazchem
http://www.ilo.org/legacy/english/protection/safework/cis/products/safetytm/tranann5.htm