Re: Connection of Hood to Fire Alarm
Actually, the 904.3.5 only requires monitoring; it doesn't say if it should be by supervisory signal or alarm signal. I think the question is whether or not the building alarm system is required to activate if the hood discharges. That is a bit more nebulous. Section 904.3.4 requires local alarms and a connection to audible alarms per 907.9.2. However, the only thing that 907.9.2 does is tell you what the decibel level should be - not if the building alarm system is required to activate.
Even in the new 2009 edition, Section 907 doesn't identify cooking hood suppression systems directly. It boils down to what NFPA 72 calls an alarm condition. Since discharge has occurred, it is considered an alarm and would normally be treated as such.
In rare situations we have asked for (and received) permission to treat the hod discharge as a supervisory signal rather than an alarm signal. This was for large facilities with open communication between areas. Instead of having a hood discharge in one corner of the building initiate evacuation by alarm, the discharge notification calls the fire department by does not initiate an alarm unless a second device activates. Thus, if the fire is not contained by the hood system, the sprinkler system will initiate the occupant notification. This was only done in large facilities where the risk for injury by crush or people movement was high enough to offset the need to immediately notify. My point is that the code isn't crystal clear which allows for this type of negotiation. Generally, activate the alarm.