Fire hazard risk methods of classification

Throughout this book the regulatory regime is referred to as Labour Code , a translation of the French Code du Travail . All countries have national regulatory codes, some of which reflect wider imperatives (eg ED directories, ILO conventions, UN standards). In adddition, there are many technical and other codes of practice or procedure produced by national or international professional, technical and industrial organisations. Exampies of the former are the reguiatory codes of the HSE and The EA in the UK, and of OSHA and ERA in the USA and of the latter, the NFPA, which is referred to extensively in this book. 

The purpose of these classifications is to enable the user to know the risk level of a substance, and for those that are related to regulations, to codify danger signals that are compulsory in order to inform users as well as carriers. There are four classifications  

This classification system allocates to substances a number between 0 (minimum danger) and 4 (maximum danger) defined by NFPA as follows  

4 substances that quickly or completely evaporate under normal pressure and at ambient temperature or that can be easily dispersed in the air and easily burnt. This level includes gas, cryogenic liquids, all liquids with a flashpoint less than 22.8°C (73°F) and boiling point less than 37.8°C (100°F). In addition, there are substances like inflammable dust that can form suspensions in air leading to explosive mixtures, as well as aerosols. These mixtures can be formed in certain environmental and activating conditions. 

2 Substances that need to be preheated to give off inflammable gaseous mixtures. This is so for liquids with flashpoints greater or equal to 37.8°C or less than 93.3°C cind solids that easily provide inflammable vapour. 

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