Classification of instability risk

Following is the technique used by the NFPA and European Union and labour regulations in order to classify instability hazard before coming back to the technical approaches. 

With regard to inflammability, NFPA coding classifies reactivity hazard into five degrees from 0 (no danger) to 4 (maximum danger), defined as follows  

4 Substances, which, by themselves, can very easily detonate or cause an explosive decomposition reaction at normal pressure and temperature. This 

Hazard identification signals XLVll, J. Chem. Educ., 45(5), pp. A413-A422,1968 and http //www.orobs.msu.edu/chemical/nfpa/reactivity. 

3 Materials or substances, which can, by themselves, detonate or cause an explosive reaction, but need a source that initiates these decompositions or reactions or need to be heated in containment. This includes substances that are sensitive to mechanical or thermal shocks at high temperature and/or pressure or that react explosively to water. 

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