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Illustrated Changes to the NEC, 2005 Edition - Part 2

Article 501

Class I Locations

501.15 Sealing and Drainage

Part II. Wiring

Text revisions clarify that when a conduit leaves a Class I, Division 2 location to an unclassified location, the required boundary seal isn't required to be explosionproof, but it must be identified for the purpose.

(B) Conduit Seals, Class I, Division 2.
(2) Conduit Boundary Seal at Unclassified Location. A conduit seal fitting must be installed in each conduit that passes from a Class I, Division 2 location into an unclassified location within 10 ft of the Class I, Division 2 area on either side of the boundary. Rigid metal conduit or threaded steel intermediate metal conduit shall be used between the sealing fitting and the point at which the conduit leaves the Division 2 location, and a threaded connection shall be used at the sealing fitting. Except for listed reducers at the conduit seal, there shall be no union, coupling, box, or fitting between the conduit seal and the point at which the conduit leaves the Division 2 location.
Figure 501-1

Author's Comment: The conduit boundary seal at unclassified locations is to prevent the passage of gases or vapors; it is not to contain explosions in the conduit system.

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