National Electrical Installation Standards

Standards as High as Your Own

Tuesday, December 6, 2022


Greetings Charlie! Love this forum. You do an excellent job. My question is regarding 300.21. There seems to be some debate on whether all wall penetrations need to be fire stopped or just penetrations through fire rated walls. Could "Substantially increased" apply to any wall penetration? Local AHJ's seem to differ a bit here as well. What is your take? Thank you! Jason Rolf


Hi Jason, thank you for the kind words, glad to hear you enjoy the CQD. Section 300.21 is made up of two parts/sentences, with the first sentence establishing the intent:

“Electrical installations in hollow spaces, vertical shafts, and ventilation or air-handling ducts shall be made so that the possible spread of fire or products of combustion will not be substantially increased”.

 The second part/sentence establishes the rule:

“Openings around electrical penetrations into or through fire-resistant-rated walls, partitions, floors, or ceilings shall be fire-stopped using approved methods to maintain the fire resistance rating.”

This would indicate that only those penetrations through fire-resistant-rated walls, ceilings, etc. need to be fire-stopped to maintain the fire-resistance-rating.

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CHARLIE TROUT: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Even though Charlie passed away in October of 2015, his work continues in spirit. NECA continues to maintain this question forum for its many subscribers in memory and recognition of all his significant contributions to making the NEC what it is today.

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