Who's Afraid of Combustible Dust? - an Update on Electrical Area Classification

The NEC has included the Zone system for electrical area classification since 2005, however the major NFPA dust standards have purposefully discouraged its use due to perceived inconsistencies with the traditional Division system.  ANSI/ISA 60079-10-2 has been the US standard for implementation of the Zone system, consistent with the IEC 60079-10-2.  Recently NFPA 499 has included guidance for electrical area classification using the Zone system, as well as clarifications necessary to unify the application of the two approaches.  The traditional Division system is compared to the Zone system, including the various definitions of combustible dust and implications for users.