To supersede the requirements of Sentence 3.2.4.7.(2) and permit manual [alarm and alert] silencing switches outside the fire alarm control unit, if silencing can only be done after the alarm signal has sounded initially for not less than 60 s.
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 alarm signal sounding for not less than 60 s] is to limit the probability that persons will not be aware of a fire situation, which could lead to delays in evacuation or moving to a safe place, which could lead to harm to persons.