To supersede the requirements of Sentence 3.2.4.6.(2) and permit manual [alarm and alert] silencing switches outside the fire alarm control unit, if silencing can only be done after the alert signal has sounded initially for not less than a certain period of time.
This [the silencing provision] is to limit the probability that voice messages will not be heard or understood, which could lead to persons not being instructed in a fire situation, which could lead to inappropriate action by such persons, which could lead to delays in evacuation or moving to a safe place, which could lead to harm to persons.
This [the alert signal sounding for not less than a certain period of time] is to limit the probability that designated persons [staff] will be unaware or misinformed of a fire situation, which could lead to: