If you have flammables on site, the first few Articles in Chapter 5 of the NEC are important to you. One question that arises in relation to these is, "What’s the difference between Zones and Divisions?"
Article 505 covers the requirements for the Zone classification system as an alternative to the Division classification system covered in Art. 500 for Class I, Zone 0, 1, and 2.
If you use the Zone system, then you must generate and maintain specific documentation that conforms to extensive specific references [505.4]. Exactly how you may classify a location depends on the properties and concentrations of the flammable substances that may be present [505.5].