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within the zone of initiation, alarm is acknowledged

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sunyaer

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Apr 21, 2022
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Toronto
The following is a screenshot from OBC Division B part 3:

1. What does "signal silence" mean? Does it mean a silence where there is no signal being transmitted to the control facilities?

2. What does "the automatic signal silence cannot occur .... within the zone of initiation" mean? Does it mean that the silence cannot occur within the area of the zone which initiated the alarm?

3. What does "is not acknowledged" in "if the alarm is not acknowledged" mean?

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This is probably referring to a two stage fire alarm system. IN those systems most sensors will trigger an "alert" to a continuously occupied location. The best example of this is in a hospital. If a sensor goes off, they don't want to evacuate the whole hospital in case it is a false alarm, so an alert is sent to someone who then investigates to see if there is a fire or not. If they confirm there is a fire (usually using a key at a manual/pull station, or if they do nothing, the fire alarm triggers into phase two, which is a full alarm.

Additionally, fire alarms a zoned to help people find where the fire may be. This also can help with evacuation procedure to prioritize occupants who are most at risk.

So, alarm cannot be silenced within the zone of initiation, they can silence the alarms in other zones, but not the one that initiated the alarm.

If the alarm is not acknowledged, this is just triggering the second stage in an alarm.
 
tmurray said:
..., so an alert is sent to someone who then investigates to see if there is a fire or not. If they confirm there is a fire (usually using a key at a manual/pull station, or if they do nothing, the fire alarm triggers into phase two, which is a full alarm.
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Click to expand...
Does the alert sound so that all occupants can hear it or is the alert only sent to staff on duty? (screenshot below shows the alert signal sounds to be heard by all occupants)

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Attachments

  • Sequencing for Modified fire alarm systems.pdf
    262.4 KB · Views: 2
CAN/ULC-S524 defines an alert signal as "an audible signal to advise designated persons of a fire emergency". Based on this definition, I would say it is not all occupants and it may not even be all staff on duty. It all depends on the occupancy and their fire response plan.
 
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