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NOTE: This is an unformatted excerpt from our online fire protection training library.

Identifying Materials & Equipment

Special Cases

The NEC provides two exceptions based on pressure piling considerations. By sealing all conduit entries to enclosures, certain materials may be treated as belonging to a less dangerous group.

"Exception No. 1:  Group D equipment shall be permitted to be used for atmospheres containing butadiene, provided all conduit runs into explosionproof equipment are provided with explosionproof seals installed within 450 mm (18 in.) of the enclosure."

"Exception No. 2:  Group C equipment shall be permitted to be used for atmospheres containing allyl glycidyl ether, n-butyl glycidyl ether, ethylene oxide, propylene oxide, and acrolein, provided all conduit runs into explosionproof equipment are provided with explosionproof seals installed within 450 mm (18 in.) of the enclosure
NOTE: This is an unformatted excerpt from our online fire protection training library.

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