Does anybody remember sub-ducts?
I recently came across a subduct in a hydraulics shaft whilst doing an inspection on a 5 storey office building. This building was designed by the old State Government Public Works Department for the former State Rivers and Water Supply commission. These can be a useful alternative to a fire damper in certain circumstances, particularly where space is limited.
AS1668.1 permits subducts to be used both in smoke spill ducts and in minor exhaust ducts. Although the detailing of the construction is slightly different the concept is essentially the same.
Image courtesy of SAI Global - Fig 3.6 of AS1668.1:1998
Subducts for minor exhaust systems are described in detail, including diagrams for installation in Section 3.6 of AS1668.1. Subducts for minor exhaust systems are described in Clause 3.6.4 of AS1668.1. Their use is essentially limited by the comment in the standard that “The sheet metal riser shall be enclosed in a shaft which may contain water supply, soil and waste services.” So gas and other combustible services, even supply and return air are out.
Tags: building permit, Building Regulations 2006, smoke spill
Good site!
Sub-ducts are to be installed as per the requirements of a fire damper or manufacturers installation detail, but it has been my experience that they are frequently not installed correctly. The compliance requirements of sub-ducts will be determined by the performance Standard nomination in the Final Fire Safety Certificate (NSW) or equivalent i.e AS16681:1991 or 1998.
The installation of fire dampers and service penetrations though out the industry leaves a lot to be desired with maintenance and passive fire contractors reaping the benefits of unwary owners or facilities managers.
It is highly recommended that new installations and/or fitouts involving essential fire safety measures have an independant compliance inspection on behalf of the owner prior to the end of the DLP and release of detention monies.