Question:
My concern is about a Fire Alarm damaged by a transient that enters from other building, passes through alarm, then is outgoing via AC electric power line. Would this alarm still report itself as failed? Apparently yes according to summary of NFPA 72. Where does NFPA 72 come from (its purpose and intent)? Is this a new standard and does it obsolete NFPA 70?

Answer: NFPA 70 and 72 coexist. 72 is the National Fire Alarm Code. 70 is the National Electrical Code. There are many other standards out there. Visit www.nfpa.org. It's very hard to install just about anything without needed to know something from more than one code. In answer to your question: If the transient passed throught the fire alarm control panel, there is a possibility that it could be knocked out without having a chance to report any failure. This is the reason for having transient protection. The hope is that the protection will hold and the alarm panel will take little or no damage.