Specification E2.2c Smoke-and-heat vents
1. Adoption of AS 2665
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To nominate AS 2665 as the basis for the installation of automatic smoke-and-heat vents, and specify its limitations.
AS 2665 is adopted as the requirement for the installation of a system of automatic smoke-and-heat vents.
Smoke-and-heat vents are dependent on the temperature of the hot smoke layer or the presence of smoke for effective operation. The area of the smoke reservoirs is, therefore, limited by AS 2665 to 1500 m2, which is smaller in size than that for mechanical smoke exhaust systems.
It is important to note that the maximum length of a smoke reservoir in a shopping mall is limited to 60 metres due to the distance people travel below a smoke layer while evacuating, having regard to the potential for smoke from a fire in a mall or adjacent specialty shop to flow into more than one reservoir.
AS 2665 requires all smoke-and-heat vents within the same reservoir to operate simultaneously to prevent the formation of stagnant regions leading to excessive cooling and downward mixing of smoke with the clear air below.
In the event of loss of power to operating mechanisms (such as actuators or solenoids), AS 2665 requires smoke-and-heat vents to fail-safe open.
Permanently open vents may be used to replace all or part of the total number of smoke-and-heat vents provided they comply with the relevant parts of AS 2665.
To specify the controls for automatic smoke-and-heat vents.
Smoke-and-heat vents installed for smoke hazard management purposes in accordance with Table E2.2b must primarily be initiated on the detection of smoke to enable early operation of the vents.
Where smoke-and-heat vents are installed in Class 7 and Class 8 buildings in accordance with C2.3(a), the operation of the vents by means of fusible links is considered adequate.
The smoke detection requirements for smoke exhaust systems are addressed in Clauses 5 and 7 of Specification E2.2a. Such smoke detection systems designed to operate smoke-and-heat vents must also activate an occupant warning system.
It is important to note that to allow manual control of the smoke exhaust system by the fire brigade, AS 2665 requires an override control to be located adjacent to the fire indicator panel.