Type NM-B nonmetallic-sheathed cable may be used for both exposed and concealed work in normally dry locations at temperatures not to exceed 90 degree Celsius with ampacity limited to that for 60 degree Celsius conductors as specified in the national electrical code 1. NM-B cable is primarily used in residential wiring as branch circuits for outlets, switches and other loads. NM-B cable may be run in air voids of masonry block or tile walls where such walls are not subject to excessive moisture or dampness. Voltage rating for NM-B cable is 600 volt.