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Maintenance testing of occupant warning sounders within apartments
Occupant warning sounders within apartments are important life safety devices, but is adequate maintenance testing being undertaken? Australian Standard AS 1851 requires practitioners to confirm that a system is performing—but, if components within an apartment are not included in testing, how can you be sure?
PHOTO: FPA AUSTRALIA
How do you test to make sure that BOWS are loud enough to wake occupants?
DAVID SLOAN
Florian Fire Consulting
A Class 2 multistorey apartment building typically requires the installation of an AS 1670.1i detection and building occupant warning system (BOWS). This is to ensure that a resident within the building can be alerted in the event of a fire and can evacuate safely.
Such a system may include detection in public areas, such as corridors, and occupant warning sounders within all apartments (or single occupancy units), with all devices connected to a fire indicator panel.
However, National Construction Codeii Specification E2.2a Clause 7 also permits the use of a BOWS that provides a minimum 100 dB(A) externally at the apartment door, from sounders located within public areas such as corridors. Although a common AS 1670.1 sounder typically provides around 105 dB(A) at 1 m, such a BOWS may have disadvantages.
In a paper on sound attenuation (reduction), Halliwell and Sultan introduced the concept of “noise reduction” (NR).iii This was defined as the difference between outdoor and required indoor sound levels. NR can be affected by many factors, including the angle at which sound strikes a partition (doors); the geometry of the room; and sound absorption from carpets, soft furnishings and so on.
AS 1670.1 specifies a minimum sound pressure level of 75 dB(A) at each apartment bedhead, with the bedroom doors being closed, which is assumed will wake the majority of sleeping occupants.
However, it cannot be assumed that external sounders in corridors will always achieve this.
Another BOWS design option is to provide sounders within the apartments themselves. By doing so, NR through closed doors (approximately 10 dB(A) per door) can be negated. This can be achieved with a sole sounder outside the bedrooms or may include an additional sounder within each bedroom (so for a two-bedroom apartment, there might be three internal sounders in total).
Fire engineers commonly request sounders to be installed in all bedrooms of some apartments as part of a fire engineered performance solution, often to justify extended travel distances in an external public corridor.
The maintenance of fire safety systems is undertaken in accordance with AS 1851,iv which includes testing of the AS 1670.1 detection and BOWS. But, if internal AS 1670.1 sounders are installed, are they ever checked as part of an external AS 1851 maintenance test?
In a two-bedroom apartment with three internal sounders, this would mean a practitioner determining that all three sounders had operated successfully.
Otherwise, if appropriate testing cannot be undertaken without having to enter every apartment, how could it always be assumed that the 75 dB(A) requirement at each bedhead was being achieved? And how could fire engineers have confidence that any performance solutions that relied, in part, on sounders within bedrooms, were functioning as assumed?
If BOWS sounders are going to be prescribed for apartments, maintenance regimes need to ensure that testing occurs within the apartments too.
If access to individual apartments is not assured, then a new way of testing sounders remotely needs to be developed. Otherwise, the contribution of a BOWS to occupant safety cannot be guaranteed.
i Standards Australia, 2018, AS 1670.1 Fire detection, warning, control and intercom systems – System design, installation and commissioning – Fire. ii National Construction Code 2019, Volume One, Amendment 1, 2021, Australian Building Codes Board, Canberra, Australia. iii Halliwell, R.E. and Sultan, M.A., 1986, Guide to Most Effective Locations for Smoke Detectors in Residential Building Building Practice Note, no. 62.,
National Research Council of Canada, Institute for Research in Construction. iv Standards Australia, 2012, AS 1851 Routine servicing of fire protection systems and equipment.
