AS 4254:2002 pdf free download.Ductwork for air-handling systems in buildings.
2.1 DUCT WORK
2.1.1 General
The construction and installation specifications in this Standard include the following:
(a) Single prescription method requirements.
(b) Alternatives.
(c) Performance requirements for specific items that are independent of illustrations, stated as depicting items representative of a class of items too broad to be comprehensively illustrated.
Regardless of pressure classifications, nothing herein is intended to preclude the use of products or methods demonstrated to the satisfaction of the specifying authority to be equivalent in performance for the particular application.
If ductwork is required to have a fire resistance level (FRL). the ductwork and applied lire protection system shall be identical to a prototype that has been submitted to a fire resistance test in accordance with AS 1530.4, or satisfies the requirements of the Building Code of Australia (BCA). This may require ductwork design to exceed the minimum requirements of this Standard.
NOTE: All ductwork should, where practicable, he installed allowing clearances for access when carrying out testing, commissioning and maintenance routines.
Where ducts penetrate walls that are required to have a FRL, salls shall be protected by fire dampers complying with AS 1682 series of Standards.
2.2 DUCT SEALING
2.2.1 General
The following are used as sealing media:
(a) Mashes Mastics are putty-like materials the plasticity of which makes them suitable for sealing where they can be moulded to suit the conformation of the area to be sealed. An acceptable ‘airtight’ seal can only he obtained when the mastic is held in a joint either by lapping the metal surfaces or by compressing the two surfaces.
(b) Liquids Liquid sealants shall be applied by brush or pump and shall be used only where they are held in the joint by lapping metal surfaces and surfaces under compression.
(c) Gaskets Gaskets shall be used to seal between two surfaces under compression, which are to be released periodically. The material for the gasket shall be chosen so that its elastic memory and compressibility suit the degree and frequency of compression at the joint to be sealed.
(d) TapeS Where adhesive tapes are used, they shall have mechanical properties equal to or better than the polyethylene tape referenced in AS/NZS 1599 (Serial Number 18) and shall be compatible with the sealant, which shall not decrease the bonding quality. Tapes shall be labelled with manufacturer’s name and the words ‘Compliant with AS 4254’ at least every 200 mm. Adhesive tapes shall not be used as the primary sealing agent connecting rigid duct to rigid duct.
Sealing media with thickness not exceeding 3 mm after its final application shall comply vith the following requirements for early fire hazard properties of materials:
When applied to internal duct surface and exposed to the air stream, sealing media shall have, when tested in accordance with AS 1530.3 a smoke development index not greater than ‘3’ (see AS 1530.3) and a spread of flame index not greater than ‘0’ (see AS 1530.3).
Sealing media with thickness exceeding 3 mm after its final application shall comply with the above requirements regardless of its location on the ductwork.AS 4254 pdf download.