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3.4.3.2.(6)
ApplicationIntent
OS3+
ObjectiveOS3 Safety in Use
Attribution
[F10-OS3.7]
Application
Application 1: 
Required exit width for exit stairs that serve interconnected floor spaces designed in accordance with Articles 3.2.8.3. to 3.2.8.9.
This applies to buildings described in Sentence 1.3.3.2.(1) of Division A that contain portions of a floor area or mezzanines that do not terminate at an exterior wall, a firewall or a vertical shaft, and are required by Clause 3.2.8.1.(1)(b) to be protected in conformance with Articles 3.2.8.3. to 3.2.8.9.
Application 2: 
This also applies to:
  • exit stairs in an assembly hall or theatre serving more than one balcony level, as stated in Sentence 3.4.3.2.(5),
  • tents and air-supported structures, as stated in Sentences 3.1.6.1.(1) and 9.10.1.2.(1), and
  • buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9], where there are openings through floors that are not protected by shafts or closures, as stated in Sentence 9.10.1.2.(6).
Exceptions: 
except:
  • where the stairs provide not less than 0.3 m2 of area of treads and landings for each occupant of the interconnected floor space, or protected floor spaces conforming to Article 3.2.8.6. are provided at each floor level, and the protected floor space on a floor level has not less than 0.5 m2 of space for each occupant of that floor level of the interconnected floor space,
  • as stated in Sentence 3.1.6.2.(1), which prohibits air-supported structures from being located above the first storey on any building,
  • as stated in 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,
  • as stated in 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,
  • as stated in Article 3.2.8.2., which applies to certain occupancies and situations,
  • as stated in Sentence 3.3.1.3.(5), which applies to rooftop enclosures,
  • as stated in Sentence 3.3.4.2.(3), which applies to dwelling units,
  • as stated in 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,
  • as stated in 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), and
  • as stated in Sentence 9.9.4.7.(1), which applies to buildings:
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Intent
Intent 1: 
To supersede the permission of Sentence 3.4.3.2.(4) not to cumulate exit widths for superimposed floor areas on the basis that all floor areas in an interconnected floor space are subject to exposure from the same fire or other untenable conditions and thus require simultaneous exiting from all floors.
This is to limit the probability that exits will be of insufficient width to permit efficient egress simultaneously from all portions of the interconnected floor space in an emergency situation, which could lead to delays in the evacuation or movement of persons to a safe place, which could lead to harm to persons.
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