Quite simply.
NFPA Standards, by definition, contain only mandatory information, beacause they are intended to be adopted as laws by local AHJs (authorities having juristiction).
NFPA 921 does not contain only mandatory information.
Here are the NFPA Offical Definintions as reported in 921:
3.2 NFPA Official Definitions.
3.2.1* Approved. Acceptable to the authority having jurisdiction.
3.2.2* Code. A standard that is an extensive compilation of provisions covering broad subject matter or that is suitable for adoption into law independently of other codes and standards.
3.2.3* Guide. A document that is advisory or informative in nature and that contains only nonmandatory provisions. A guide may contain mandatory statements such as when a guide can be used, but the document as a whole is not suitable for adoption into law.
3.2.4* Recommended Practice. A document that is similar in content and structure to a code or standard but that contains only nonmandatory provisions using the word “should” to indicate recommendations in the body of the text.
3.2.5* Standard. A document, the main text of which contains only mandatory provisions using the word “shall” to indicate requirements and which is in a form generally suitable for mandatory reference by another standard or code or for adoption into law. Nonmandatory provisions shall be located in an appendix or annex, footnote, or fine-print note and are not to be considered a part of the requirements of a standard.
This has been reported on the Forum many, many, many times.
What is so hard to understand about that? Could it be that if individuals admit that they understand the difference between an NFPA Standard, and a "standard of care," or a "standard of good practice," or an ASTM Sandard Practice, or a UL Standard, that they then cannot keep arging about it?
Pat Kennedy, CFEI, CFPS, MIFireE
Fire and Explosion Analyst
Sarasota, Florida
[
www.kennedy-fire.com]