OWS vs EWIS: What's the Difference? A Guide for Strata Buildings

Estimated reading time: 9 minutes

When discussing fire detection and alarm systems in strata buildings, the terms Occupant Warning System (OWS) and Emergency Warning and Intercommunication System (EWIS) are often used interchangeably.

Although the terms are commonly used that way, they do not necessarily describe the same system. Both provide occupant warning, but an EWIS adds evacuation-control and intercommunication functions that an OWS does not, and the two arrangements are generally designed to different Australian Standards.

Understanding the difference is important because the type of warning system installed within a building can have a significant impact on building operation, emergency procedures, maintenance requirements, future replacement and modification works, and project costs.

For many strata committees, the distinction only becomes apparent when ageing equipment requires replacement, significant modifications are being considered, or competing proposals are received for fire system works.

Key Takeaways

✔ Both an Occupant Warning System (OWS) and an Emergency Warning and Intercommunication System (EWIS) provide occupant warning; an EWIS adds additional evacuation-control and intercommunication functions.

✔ An OWS does not become an EWIS simply because it uses speakers, recorded messages or an emergency microphone.

✔ An OWS normally delivers the building's predetermined warning response and cannot phase or delay warning between different areas.

✔ An EWIS provides separate emergency-zone controls and communication facilities that can be used to manage a more complex evacuation.

✔ Warden Intercommunication Points and separately controlled emergency zones are key features associated with an EWIS.

Not familiar with some of the terminology used in this article? Visit our Fire Detection & Alarm Systems Glossary for plain-English explanations of common terms.

Feature	OWS	EWIS
Provides occupant warning	✔	✔
Can use speakers	✔	✔
Can provide recorded warning messages	✔	✔
Can incorporate an emergency microphone	✔	✔
Can use visual alarm devices	✔	✔
Can use ordinary electronic sounders for audible warning	✔	✘
Separately controlled emergency zones	✘	✔
Phased or delayed warning between emergency zones	✘	✔
Live speech can be directed to selected emergency zones	✘	✔
Warden intercommunication facilities	✘	✔

Typical system capabilities only. The equipment and functions required for a particular building depend on its applicable requirements and approved design.

The key difference

Both an Occupant Warning System (OWS) and an Emergency Warning and Intercommunication System (EWIS) warn building occupants when an emergency occurs.

An OWS delivers the building's predetermined warning response when the relevant alarm condition is received. The trigger may come from automatic detection, sprinkler alarm equipment, a manual control or another approved fire-system input. Under AS 1670.1, the warning cannot be phased or delayed between different areas of the building.

An EWIS adds separate emergency-zone control and intercommunication. This allows different emergency zones to receive different warning states or instructions, live announcements to be directed to selected areas and wardens to communicate with the emergency control point.

Speakers, recorded messages or even an emergency microphone do not by themselves make an OWS an EWIS. The difference is the additional evacuation-management and intercommunication functions.

What Is an Occupant Warning System (OWS)?

An Occupant Warning System provides the building's predetermined occupant warning response when the relevant alarm condition is received. The trigger does not have to be an automatic smoke detector; in some buildings it may come from sprinkler alarm equipment or another approved fire-system input.

Depending on the building and equipment, an OWS may use:

• Electronic sounders or bells

• Speakers

• Warning and evacuation tones

• Recorded emergency messages

• Visual alarm devices

• An emergency microphone or other manual controls

An OWS can still be quite sophisticated. It may use speakers, recorded messages, visual alarm devices and an emergency microphone without becoming an EWIS.

Speaker circuits or transmission paths may be separately monitored for faults. That separation is for monitoring purposes; it does not allow different areas to receive different warning responses or to be evacuated at different times.

The warning equipment may be incorporated into the fire indicator panel (FIP) or installed in a separate cabinet connected to it. Where speakers are used, the associated amplifiers may also be integral with the panel or installed as separate occupant-warning equipment.

The design and installation requirements for an OWS are generally addressed by AS 1670.1, subject to the edition and compliance requirements applicable to the building.

What Is an Emergency Warning and Intercommunication System (EWIS)?

An Emergency Warning and Intercommunication System also provides occupant warning, but adds the emergency-zone controls and communication facilities needed to manage a more complex evacuation.

It may operate automatically when the relevant fire alarm condition is received, while also allowing authorised personnel or emergency responders to control warning signals and instructions across different emergency zones.

Depending on the building's evacuation strategy, an EWIS may provide:

• Automatic alert and evacuation sequences

• Separate control of individual emergency zones

• Phased or staged evacuation

• Alert and evacuation tones

• Recorded emergency messages

• Live announcements to selected areas

• An emergency microphone at the control panel

• Warden Intercommunication Points

• Two-way communication between wardens and the emergency control point

• Dedicated amplifiers, power supplies and standby batteries

An EWIS is controlled from a Master Emergency Control Panel (MECP) and may also include other Emergency Control Panels (ECPs). These controls are explained later in this article.

The design and installation requirements are generally addressed by AS 1670.4, subject to the requirements applicable to the building.

Why Do Some Buildings Require an EWIS?

Not every building requires an EWIS. The buildings that do generally have evacuation arrangements that can be more complex than simply sounding one alarm everywhere.

Under the NCC Deemed-to-Satisfy provisions, an EWIS complying with AS 1670.4 is required in situations including:

• Buildings with an effective height of more than 25 metres

• Certain multi-storey Class 3 accommodation used for children, aged people or people with a disability

• Residential care buildings

• Larger or multi-storey healthcare buildings

• Taller school buildings

• Larger or multi-storey theatres, public halls and similar assembly buildings

These buildings may need selected areas placed on alert, particular levels or zones evacuated first, live instructions broadcast, or wardens able to communicate with the emergency control point. The EWIS provides the facilities needed to support the approved evacuation strategy.

These current NCC provisions should not be read as automatically imposing a retrospective EWIS upgrade on every existing building. Requirements for an existing building depend on matters such as its approval history, Fire Safety Schedule, fire engineering documentation, any Fire Safety Orders and the scope of proposed work.

Why Are the Terms Used Interchangeably?

Specifications, drawings and quotations sometimes use “EWIS” loosely for any speaker-based occupant warning system. But speakers, evacuation tones, recorded messages or an emergency microphone do not by themselves make a complete EWIS.

Conversely, equipment capable of providing EWIS functions may sometimes be installed and configured only as an OWS. The label alone is therefore not enough: the Fire Safety Schedule, approved design and any applicable fire engineering documentation should establish the warning and communication functions required.

This becomes particularly important when comparing quotations, because one proposal may allow for a complete EWIS while another may only include a speaker-based OWS.

Speakers, Sounders and Visual Alarm Devices

Speakers and visual alarm devices (VADs), commonly called strobes, may be used with either an OWS or an EWIS. An OWS may also use ordinary electronic sounders that generate preset warning tones. An EWIS uses speakers because it must be capable of broadcasting warning tones, recorded messages and live instructions into selected emergency zones.

An OWS with speakers and an emergency microphone may be capable of live speech throughout the area served, but that still does not provide separate emergency-zone control. A microphone also does not by itself establish that the system has been designed for intelligible live emergency speech; audibility and speech intelligibility are separate design considerations.

The images below show typical examples of warning devices.

Recessed speaker - the red back-can is concealed above the ceiling	Surface-mounted speaker	Horn speaker — often used in car parks, plant areas and larger spaces
Visual Alarm Device (VAD) commonly called a strobe	Electronic sounder—provides tone-based warning in an OWS

Device appearance varies by manufacturer and application. Speakers and VADs may form part of either system, while an ordinary electronic sounder provides tone-based warning in an OWS. Individual devices should not be relied upon by themselves to identify the building's complete warning system.

What Is a Warden Intercommunication Point (WIP)?

The red phones found throughout some buildings are Warden Intercommunication Points (WIPs), commonly called WIP phones. They provide two-way communication between wardens, emergency personnel and the emergency control point.

A WIP is often located beside a Manual Call Point (MCP), but the devices do different jobs: the WIP is for communication, while the MCP manually initiates a fire alarm. MCPs are not unique to EWIS, whereas WIPs are a key part of EWIS intercommunication.

What Is an EWIS Master Emergency Control Panel?

Buildings equipped with an EWIS typically include a Master Emergency Control Panel (MECP), which provides the main controls for emergency warning and intercommunication.

The MECP allows authorised personnel to:

• Monitor emergency communication functions

• Broadcast emergency messages

• Control evacuation zones

• Communicate with wardens

The MECP operates alongside the FIP but performs a different role. The FIP monitors and controls the fire detection system; the EWIS manages occupant warning and emergency communications. The two functions may be housed in separate panels or combined within the same physical cabinet.

EWIS panels vary in appearance depending on the manufacturer, model and system configuration. Below are three EWIS panels commonly encountered in Australia. These are examples only.

Ampac EvacUElite	FireSense ECS-16 — from Honeywell’s Notifier product family	Vigilant QE20

Although the layout varies between manufacturers, common features include:

• Controls and indicators for the building's emergency zones

• Alert, Evacuate and public-address controls

• An emergency microphone for selected zones or the whole building

• A master WIP handset and call indicators

• Fault, isolation and equipment-status indicators

The repeated emergency-zone controls and communication equipment are often the clearest visual clues that a panel is an EWIS control panel, although appearance alone is not conclusive because the FIP and EWIS may be installed together or combined in one cabinet.

What Is Phased Evacuation?

Phased evacuation allows different emergency zones to receive different warning states or instructions. Depending on the approved strategy, one zone may be evacuated while another remains on alert, and authorised personnel can change the warning as the incident develops. For example, a high-rise sequence might evacuate the fire floor, two floors above and one below before progressing to other levels.

An OWS installed under AS 1670.1 does not provide this separate emergency-zone control; it delivers the building's predetermined warning response throughout the area served.

Why OWS vs EWIS Matters When Replacing a Fire Panel

This distinction becomes particularly important when a FIP or warning system is being replaced. A project described simply as “fire panel replacement” may also involve separate or integrated occupant-warning or EWIS equipment.

A speaker-based OWS may use some of the same types of equipment as an EWIS. The additional EWIS scope comes from the functions that must be retained, particularly separate emergency-zone control, managed evacuation functions and, where required, warden intercommunication.

Two quotations for “fire panel replacement” may therefore include different scopes. Before comparing price, confirm that each proposal retains the warning and communication functions the building is required to have.

Questions to Ask Before Approving a Fire Panel Replacement

If your building is considering a fire panel replacement, ask:

1. Is the building required to have an OWS or an EWIS, and what documentation establishes this?

2. Is the warning equipment incorporated into the FIP or installed separately?

3. Does the proposal retain all required warning and communication functions, including emergency-zone control and WIPs where applicable?

4. Is any existing OWS or EWIS equipment obsolete or excluded from the proposal?

5. What testing, commissioning or staging is required while the system is being replaced?

Final Thoughts

OWS and EWIS are often used interchangeably, but they do not necessarily provide the same functions. Both provide occupant warning; an EWIS adds the emergency-zone control and intercommunication facilities needed to actively manage a more complex evacuation.

Speakers, recorded messages or an emergency microphone do not by themselves make an OWS an EWIS. The important question is what warning, evacuation and communication functions the building is actually required to have.

Want us to cover another topic?

We'll continue adding new fire detection and alarm system topics over time. If there's a question or topic you'd like us to explain, send your suggestion to info@fcfire.com.au.

About the Author

This article was prepared by Full Circle Fire, specialists in fire detection and alarm systems with more than 30 years’ experience delivering maintenance, upgrades and replacement of obsolete fire detection equipment across NSW.

Important Information

This article provides general information only and is not intended to replace advice based on the specific fire safety systems, approved documentation, building design or regulatory requirements applicable to an individual property.