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Operation of a Warning System

A warning system can include any of the following, emergency warning system, building occupant warning system (also known as an occupant warning system) or sound system for emergency purposes. The operation and emergency warning signals of a warning system are set out in the National Construction Code and a number of Australian Standards depending on the approved design including AS1670.1 and AS1670.4 and AS2220 (now obsolete).

QE90 Emergency Warning System EWIS

According to the National Construction Code (NCC) and Australian Standards, an emergency warning system forms part of the life-safety systems of a buidling and is generally required to safeguard occupants from injury by being made aware of an emergency1. This is achieved by ensuring by adequate means by (1) proving warning to occupants to evacuate; (2) and manage the evacuation process2.

The term emergency warning system is used in this article as a generic term used to describe three types of systems described in the National Construction Code (NCC) as follows;

An emergency warning system operates by simultaneously broadcasing of a fire alarm condition to all required occupied spaces of the building alerting the occupants of a in an emergency using audible alarm devices or a warning message or (alert signal or evacuate signal) signal over a network of monitored loudspeakers.

  • 1

    Australian Building Codes Board (ABCB), National Construction Code (NCC) 2022, Objective E4O1, p. 261.

  • 2

    Australian Building Codes Board (ABCB), National Construction Code (NCC) 2022, Functional Statement E4F1, p. 261.

  • 3

    The term Building Occupant Warning System is used in the National Construction Code in Specification 17 (S17C8) for certain Class 2, 3, 4, 9a and 9c buildings through all occupied areas to comply with Specification 20 (S20C7) and clause 3.22 of AS 1670.1.

Alarm or Warning System Signals

Now that we know there is a difference between a Building Occupant Warning System (Clause 3.22, AS1670.1) and an Emergency Warning System (AS 1670.4), we can now discuss the requirements for the alarm or warning signals employed by these systems.

Building Occupant Warning System

Other than an Emergency Warning System (AS1670.4), according to Clause 3.22, AS 1670.1, a building occupant warning system can comprise one of the following;

  • EWCIE in accordance with AS 4428.16, connected to compatible loudspeakers conforming to AS ISO 7240.24; or
  • Audible alarm devices conforming to AS ISO 7240.3

Where a building occupant warning system is used, the following requirements apply;

  1. the evacuation signal may not be preceded by an alert signal without the approval of the Emergency Control Organisation (ECO) and unless loudspeaker transmission paths have been installed in accordance with AS 1670.4; and
    transmission paths have been installed in accordance with AS 1670.4; and
  2. broadcast to all occupied space simultaneously unless loudspeaker transmission paths have been installed in accordance with AS 1670.4 and phased in accordance with the emergency management plan; and
  3. be in accordance with ISO 82011; and
  4. not be subject to any time delay after the occurrence of a fire alarm condition; and
  5. be synchronized throughout an area and adjacent area except where the sound pressure level from an adjacent area is at least 30 dB lower; and
  6. include words ā€œFireā€ and ā€œEvacuateā€, or a pre-recorded speech message, where an EWCIE is used.

A Building Occupant Warning System (BOWS), defined in Clause 3.22 of AS 1670.1, uses either an EWCIE (AS 4428.16) with compatible loudspeakers (AS ISO 7240.24) or audible alarm devices (AS ISO 7240.3).

These systems must broadcast evacuation signals promptly, without any time delay after a fire alarm condition, and synchronously. The system must meet ISO 8201 standards and ensure clear messaging with ā€œFireā€ and ā€œEvacuateā€ or pre-recorded speech.

Emergency Warning System

An emergency warning system may comprise a visual and/or emergency warning signal (incorporating an alert 2 signal and/or evacuate3 signal). These systems may also incorporate a phased structured and sequential warning signals in different areas of a building in accordance with an emergency management plan.

The emergency warning system (EWS) shall be initiated by ā€”

  1. an automatic emergency detection system (EDS) where it is required to be connected to the EWS;
  2. white emergency evacuation manual call points4 (MCP) where provided, typically adjacent to each warden intercom point (WIP); and
  3. manual controls provided by the EWCIE.

Where the investigation of an alarm signal is provided by the emergency evacuation plan (emergency plan), the emergency warning condition may be delayed for a maximum of 10 minutes, prior to commencing the normal emergency condition.

Alert Signal

An alert signal must operate until manually cancelled or automatically replaced by an evacuate signal5 if no manual action is taken within the time specified in the emergency management plan, which must not exceed 10 minutes.

Evacuate Signal

The evacuate signal must be broadcast within 10 minutes of a fire alarm, including delays specified in Clauses 4.3 and 4.4. It should cover all emergency zones simultaneously unless a phased evacuation is used, starting with the zone where the emergency is detected.

For buildings over 25 m in height, alert and phased evacuation signals should account for exiting methods, occupant characteristics, and building design, in consultation with the ECO.

Visual Alarm Signals

Visual alarm devices (VADs) are required in areas for persons with hearing impairments, high-noise environments (over 85 dB), where hearing protection is worn, or where audible warnings are not used (e.g., studios, surgical theatres).

VADs must be synchronised if multiple devices are visible, labelled with ā€œEVACUATEā€ in 15 mm-high contrasting letters, and installed per specified spacing.

Coverage includes circulation spaces in car parks. Designs should consider combining visual, tactile, or other warning devices for inclusivity.

  • 1

    ISO 8201:2017 specifies the requirements for an audible emergency evacuation signal intended to indicate without ambiguity, to all persons within the reception area of the signal, that an emergency situation (fire, gas leaks, explosion, nuclear radiation, etc.) requires immediate evacuation. ISO 8201:2017 is not applicable to warning signals, to signals for public disaster control or to alarm systems on board ships or in outdoor moving vehicles, such as police cars, fire engines and ambulances.

  • 2

    An alert signal is an audible signal, a visual signal, a tactile signal or any combination of these, that alerts designated
    chief and area/floor wardens of a hazardous or dangerous situation.

  • 3

    An evacuate signal an audible signal, a visual signal, a tactile signal or any combination of these that indicates the need for the immediate evacuation of an emergency zone.

  • 4

    A fire detection and alarm system (red) manual call point connected to the FDCIE in accordance with AS 1670.1 and installed in the above locations satisfies the requirements of Clause 4.2.2(b) of AS 1670.4.

  • 5

    The evacuate signal is to only be preceded by the alert signal specified in AS 4428.16 for the purpose of alerting fire wardens nominated in the emergency control plan to obtain and give instruction for the occupant to prepare for evacuation.

FeatureBuilding Occupant Warning SystemEmergency Warning System
Operative StandardAS 1670.1AS 1670.4
Alert SignalNo9Yes
Evacuate SignalYesYes
Emergency Warning Signal DelayNoAlert Signal < 10 Minutes and Evacuate Signal within 10 minutes of a fire alarm, including delays.
Phased EvacuationNo, broadcast to all occupied space simultaneously.Yes
  • 9

    Unless specified as part of the emergency management plan by the Emergency Control Organisation.

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