I was parsing the article on household fire warning systems and noticed NFPA has resolved an issue we used to run up against with AHJ's now and then. If a customer's electrician had already wired the house for smoke alarms but the client wanted monitoring for fire, I would suggest adding a few well-placed "duplicate" detectors to the alarm system. It's fairly common practice. But sometimes an AHJ would insist that if there were *any* system smokes added, we had to install a complete fire alarm system. Customers would balk at the cost and stay with unmonitored 110/9 Volt smokes.
Anyway, 2010 code says it's not necessary. It's spelled out in such a way that there's no room for misunderstanding, even by someone like the guy Jim told where to put his regulations.
- The required minimum number and location of smoke detection devices shall be satisfied (independently) through the installation of smoke alarms. [snip] The installation of additional system based smoke detectors, including partial or complete duplication [snip] shall be permitted.
#2 is the exact reversal of #1. If you install system-based smokes up to code requirements, you can add more of the same, add independent smoke alarms, etc. No harm, no foul.
29.3.4 Goes on to allow the addition of "supplementary" functions, including extending the alarm beyond the residency, as long as it doesn't interfere with the performance requirements.I didn't get the 2007 release so maybe this is old news but it was nice seeing they fixed the issue.