Ok, I am mostly just asking because I am curious. My High School is currently under construction, so we are prone to many false alarms. In fact, we have had 3 false alarms within the past 2 weeks. I’m wondering if it would be allowed for them to change the system to a 2 stage, so they can prevent full evacuation if necessary. Being it is a school, if we are in full alarm, we do have to evacuate each time. I just feel like if we set up 2 stage, and the construction company gets dust in a detector AGAIN, we can silence the system before we run into problems, and if there is a fire, we can get us all out. I am not sure if this is even allowed in a public school… Does anyone know?
Side note: I live in between the fire station and my school. I just heard fire trucks heading that way again. I would not be surprised if this is the case considering we have had 3 false alarms during the school day, and the construction company is there much longer.
I remember at my middle school a long time ago, something kept setting off a smoke detector; it might have been a ground fault or whatever. Once a few false alarms occurred in one day, the fire department silenced the alarm and left it silenced for (I’m not joking) at least 2 months. The strobes didn’t flash because there was no audible silence, but the panel displayed the condition for a looooong time.
Considering we have never had a fire in any part of our school district, I probably wouldn’t care! Granted, that isn’t to say it could never happen, but the chances are a lot less likely than they make it out to be during Fire Drills and such…
IMO, I think that a 2 stage system in any school is unnecessary. Plus, with 2 stage systems, the smoke/heat detectors are usually set up so that they automatically put the system in the second stage. The pull stations are the only ones that can set off the first stage (I believe).
Either way, I’m pretty sure the fire department has to come out when either stage is set off. I remember that, from a time I was staying in a hotel with a 2 stage system. Someone pulled the alarm twice in the same day, once at 6am and the other time at 11pm. Each time, the system never got into second stage, but the fire dept. had to respond to both calls.
During construction at my school, they where not allowed to cover or disable and smoke detectors in the area where they where working. This was the cause for three false alarms. The alarm tech said since it was a public building, they couldn’t cover or disable them. Has anyone ever heard of that rule (this is in California)
Other then a special hazard system, it is very rare to find a “two stage” fire alarm system for general alarm applications. Now, you could have a verification or pre-alarm feature built into a system that would delay the activation of the alarm, but from what I understand, these are getting rare. I only know of one building that would have something close to a two stage system - although I really wouldn’t call it that. There is a local shopping mall that would constantly have false alarms. Smoke detectors were located throughout the building; common area corridors, service corridors, food court area, restrooms, mechanical rooms, including inside the retail stores both front showroom, back stock room, and restrooms. Any stupid thing would set these things off. The decision was made with the blessing of the AHJ to reprogram the system so that all smoke & heat detectors would initiate a supervisory condition at the fire alarm panel. Mall security would then investigate and determine if there was an actual fire event that required evacuation. Several requirements were necessary for this to be approved:
1.) Building had to be 100% protected by a sprinkler system - waterflow switches would automatically activate the alarm
2.) Building had to be staffed 24/7 with someone in the security command center at all times - not a problem because mall security was there 24/7 anyway
3.) Pull station added in the security command center to activate the alarm if needed
4.) Procedures put in place for responding to all smoke or heat detector activations
So it CAN be done. Now, should it be done depends on the situation. For something as simple as construction - the simplest thing to do is remove the detectors in the area under construction, but that can be a problem if the area is still being occupied by the public. I am not a big fan of bagging detectors. Too easy to forget about the bags and I’ve seen them left in place for months after the construction is finished. And by rights, you can only bag them during active construction - at the end of the day, the bags must come off. At least if you pull detectors, on an addressable system, you’ll have the 10 or so troubles for those missing detectors to “remind” someone they need to go back up. NFPA72 actually addresses devices in an area under construction and recommends protecting the devices to reduce false alarms or throwing off detector sensitivity.
Another option is Positive Alarm Sequence. Here is the sequence of operation description in NFPA 72 2007.
6.8.1.3 Positive Alarm Sequence.
6.8.1.3.1 Systems that have positive alarm features complying with 6.8.1.3 shall be permitted if approved by the authority having jurisdiction.
6.8.1.3.1.1 The signal from an automatic fire detection device selected for positive alarm sequence operation shall be acknowledged at the fire alarm control unit by trained personnel within 15 seconds of annunciation in order to initiate the alarm investigation phase. If the signal is not acknowledged within 15 seconds, notification signals in accordance with the building evacuation or relocation plan and remote signals shall be automatically and immediately activated.
6.8.1.3.1.2 Trained personnel shall have up to 180 seconds during the alarm investigation phase to evaluate the fire condition and reset the system. If the system is not reset during the investigation phase, notification signals in accordance with the building evacuation or relocation plan and remote signals shall be automatically and immediately activated.
6.8.1.3.2 If a second automatic fire detector selected for positive alarm sequence is actuated during the alarm investigation phase, notification signals in accordance with the building evacuation or relocation plan and remote signals shall be automatically and immediately activated.
6.8.1.3.3 If any other initiating device is actuated, notification signals in accordance with the building evacuation or relocation plan and remote signals shall be automatically and immediately activated.
6.8.1.3.4* The system shall provide means for bypassing the positive alarm sequence.
A.6.8.1.3.4 The bypass means is intended to enable automatic or manual day, night, and weekend operation.
It’s interesting to see the differences between the United States and Canada regarding two-stage systems. I was aware that the requirements for such setups were different in both countries, but I didn’t know they were considered that rare south of the border. This seems kind of weird since “true” two-stage systems are absolutely everywhere around here, being used in both older and new installations.
Granted, that isn’t to say it could never happen, but the chances are a lot less likely than they make it out to be during Fire Drills and such…