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3.4.5.1.(4)
ApplicationIntent
OS3
ObjectiveOS3 Safety in Use
Attribution
[F10,F81-OS3.7]
Application
Application 1: 
Electrical circuits serving exit signs required by Sentence 3.4.5.1.(1) for exit doors, where:
This applies to floor areas that are intended for occupancy, including mezzanines as stated in Sentence 3.4.2.2.(1), in buildings described in Sentence 1.3.3.2.(1) of Division A.
Application 2: 
This also applies to:
  • exit signs placed over, or adjacent to, egress doorways from certain rooms, as stated in Sentence 3.4.5.1.(6), and
  • tents and air-supported structures, as stated in Sentences 3.1.6.1.(1) and 9.10.1.2.(1).
Exceptions: 
except as stated in:
  • Sentence 3.1.6.2.(1), which prohibits air-supported structures from being located above the first storey on any building,
  • Sentence 3.1.6.2.(2), which prohibits air-supported structures from being used for classrooms or for Groups B, C, or Group F, Division 1 major occupancies,
  • Sentence 3.1.6.2.(3), which requires air-supported structures to be designed as open floor spaces without interior walls, mezzanines, intermediate floors or similar construction,
  • Sentence 3.3.1.3.(5), which applies to rooftop enclosures,
  • Sentence 3.4.2.2.(2), which applies to mezzanines that:
    • are not required to terminate at a vertical fire separation [see Article 3.2.8.1.],
    • are not intended for an occupant load more than 60,
    • do not exceed the area limits for rooms and suites in Table 3.4.2.2., and
    • have limited travel distances to egress doors or stairs, and
  • Sentence 3.4.2.2.(3), which applies to at least half of the required means of egress from a mezzanine if the mezzanine is not required to terminate at a fire separation as permitted by Sentence 3.2.8.2.(1).
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Intent
Intent 1: 
To limit the probability that electrical circuits for the illumination of exit signs will not operate properly [e.g. due to normal power failure, or will fail or be disconnected due to deficiencies with other non-emergency electrical equipment], which could lead to the exit signs not being illuminated in an emergency situation, which could lead to exit locations not being readily identified, which could lead to delays in the evacuation or movement of persons to a safe place, which could lead to harm to persons.
Intent 2: 
To direct Code users to Sentence 3.2.7.4.(1).
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