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

Introduction to the NEC

Language Conventions

Mandatory and Permissive Rules

Section 90.5

Section 90.5 addresses language conventions. These very specific wordings are universal throughout the National Electrical Code.


Mandatory rules can be easily identified because they always use the terms "shall" or "shall not."

Permissive rules use the terms "shall not be required" or "shall be permitted." These rules do imply a responsibility of the person enforcing the code to make a determination.

The NEC considers these rules to be permissions rather than requirements, saying "here's something you can do, but you're not necessarily required to" or "here's something that you're permitted to do, but you don't necessarily have to."  However, this is dependent on a point of view. To an inspector, these permissive rules may say “here is something you must allow,” or “here is something you may permit but cannot require.”

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

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