Areas previously classified as Class I, Division 1 or 2 may be reclassified as Class I, Zone 0, 1, or 2 in order to use zone protection techniques and wiring methods Wiring methods permitted in areas classified by zone are essentially the same as those permitted in areas classified by division.. However, all of the area classified due to a single vapor or gas source must be reclassified if any part of that area is to be reclassified.