1999, all references to the zone concept of

Photo 9. Westerberg Apparatus for Determining MaximumExperimental Safe Gap (MESG)
UNDERSTANDING THE ZONE AREA CLASSIFICATION METHOD IN THE
NEC 

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cal that has a low autoignition temperature, the elec-trical equipment is just one of many items that couldbe located in the area and be a concern for causingpossible ignition of the material.
Conclusion
By providing the user with an optional method for areaclassification and an expanded number of equipmentoptions, the
 NEC 
 has become a more global and pro-gressive document. It has also expanded the ability of manufacturers to enter into the global market in a morecompetitive way.