Fire Alarm Systems 

Fire Alarm Systems

A fire alarm system is an active fire protection system that automatically (or manually) detects a fire, or the effects of fire, and performs one or more of the following functions: • warns the building occupants via audible (and possibly visual) alerting devices 

  • automatically summons the fire service (if remotely connected) 
  • indicates the location/zone of the activated detector or manual call point 
  • self-supervises for fault conditions 
  • resists false activation due to typical non-fire phenomena 
  • initiates ancillary fire-related control functions in the building (e.g. lift recall, air conditioning shutdown, smoke-stop door release). 

A fire alarm system will typically include:

  • manual call points
  • smoke and/or heat detectors
  • control and indicating equipment
  • fire alerting devices
  • safety control outputs
  • power supplies and batteries
  • interconnection wiring.

If connected to a remote receiving centre it will also include remote signalling equipment.

The protected premises will generally be subdivided into detection “Zones”. The area of a Zone is typically limited to what can readily be searched by a fire fighter in a short period of time. 

An indication of the fire’s approximate location will be provided to attending fire fighters on an “index” map of the building. Analogue Addressable Systems are also able to display a text description of the location of the activated detector or manual call point.

Fire Alarm System Design

The overall design objective of a fire detection and alarm system is to detect fire as early as possible. However it also needs to resist environmental influences and other potential sources of false activation. Once a fire is detected, the actions taken by the system must be consistent with the building’s overall design, its evacuation plan, and the integrated fire protection strategy for the premises.

For all but the simplest of buildings and risks, fire alarm system design is a specialized activity. It should be performed by a competent engineer with experience in fire protection, and who is trade-certified to act in this capacity. The overall fire safety design for a building is usually done in conjunction with the Architect’s design team during the design phase of the building project, and detailed in a “fire report.” The detailed component selection and final equipment layout and configuration/programming for a fire alarm system is typically performed by a certified fire alarm contractor, in accordance with the requirements of the fire report, during the building’s construction and fit-out phases. 

The design of building fire alarm systems in New Zealand is almost always required to be in compliance with New Zealand Standard NZS 4512:2010 Fire Detection and Alarm Systems in Buildings. This national standard covers design, installation, extension, modification, commissioning, testing and maintenance. It also sets down minimum levels of trade qualification for those working on fire alarm systems, and requires independent third-party inspection/audit of all new systems, and all significant system alterations and extensions. 

NZS 4512:2010 is the only “Acceptable Solution” for fire detection and alarm systems under the NZ Building Code Compliance Documents. Confirmation by an independent third party inspector of full compliance with this standard generally ensures acceptance under the Building Code regime by the Building Consent Authority (local council). Alternative “Engineered Solutions” are permitted, however these require a building-specific Professional Fire Engineer’s design which must undergo a series of professional reviews in order to be accepted by the Building Consent Authority. In general, such engineered solutions are invoked to allow trade-offs between one compliance parameter and another, or to accommodate unusual building features or occupancy. 

Extensions of existing systems should be performed with the same attention to design, but must also consider the capabilith of the originally-installed fire alarm system. The Standard has strict rules about the intermixing of system components, so the equipment used for extensions will generally need to have listed compatibility with the existing equipment. NZS 4512:2010 also has requirements for independent third party inspection of significant system extensions (adding zones or changing the control panel).

Detection Devices

Fire alarm systems have input devices connected to them to detect fire or smoke. Below is a list of common detection devices found on a fire alarm system: 

  • Manual Call Points – devices to allow people to manually activate the fire alarm. These are usually located near exits and on exit routes within the premises so that building occupants will be able to locate one within a reasonable travel distance after discovering a fire. Manual call points must be at least 85mm x 85mm, be coloured red, and have operating instructions. New Zealand requires two-stage operation (either “the breaking or displacing of a frangible or resettable element followed by the manual operation of a switch” or “the opening of a transparent cover or flap followed by the breaking or displacing of a frangible or resettable element”). 
  • Heat Detectors – devices which are designed to operate when the temperature or rate-of-rise of temperature exceeds a predetermined value. These are most commonly based around either a simple bi-metal thermostatic switch, or a thermistor-based electronic circuit. Eutectic alloy (low melting point metal) devices were used historically, but are now prohibited for new installations. Specialised heat detection technologies also include thermoplastic cable (shorts when the covering plastic melts) and fibre-optic based time domain reflectometry systems (particularly applicable for tunnels). 
  • Smoke Detectors – devices which detect visible or invisible products of combustion, usually emitted prior to the flaming stage. These are most typically point type devices operating on photoelectric (light-scattering) or ionization chamber principles. Other common smoke detector types include: projected beam (“linear”) smoke detectors and air-sampling (“aspirated”) smoke detectors. Smoke detectors can be very sensitive, so precautions may need to be taken to avoid false activations. 
  • Duct Detectors – smoke detectors installed in special housings are able to sample the air from a ventilation duct. These are generally used to trigger automatic precautions to prevent an air-handling system from spreading smoke around a building.
  • Carbon Monoxide Fire Detectors – devices which detect the poisonous carbon monoxide (CO) gas produced by smouldering fires. CO fire detectors are primarily used in life safety applications (e.g. sleeping occupancies). For the highest level of life safety CO detectors are usually employed in conjunction with heat or other smoke detection (e.g. multi-sensor detectors), or sprinklers. NOTE: These should not be confused with residential Carbon Monoxide alarms used to detect CO produced by faulty gas heating appliances.
  • Flame Detectors – devices which detect the infrared or ultraviolet radiation from a flaming fire. These are most typically used in commercial and industrial applications where a fast flaming fire can be expected (e.g. aircraft hangar, fuel storage depot). Unlike many other detection types, solar-blind flame detectors can also be used outdoors. 
  • Water Flow Switches – devices which detect when water is flowing through the fire sprinkler system. These will typically indicate on the zone index of the fire alarm system to assist fire fighters in locating the source of a fire, but are not generally permitted to initiate alerting (building evacuation) or a brigade call. 
  • Sprinkler System Alarm Valve – the main alarm output from a fire sprinkler system will generally indicate on the zone index of a fire alarm system and initiate alerting (general building evacuation). The sprinkler system will typically be required to have its own remote connection to the fire brigade. 

Multiple Sensor Detectors – recent advances in technology have allowed for multiple detection principles (combinations of: heat, smoke, CO, flame) to be incorporated into one detector. These so-called “multi-sensor detectors” are becoming increasingly common. Their particular attractions are enhanced detection performance combined with better immunity to false activations (nuisance alarms).

Alerting Devices

The days of fire alarm bells are well and truly gone for new installations, although bells and sirens may still be present in historical systems. For new installations, a specific standard “rising whoop” tone is now mandatory, with an interspersed verbal message (except for very small buildings). The voice message will typically be something like “Evacuate the building using the nearest fire exit”, and provides positive direction to building occupants. 

Although point-type sounders are available to produce this standard alerting signal, it is now most common for a central tone and voice generator/amplifier to be located at the fire alarm control panel, with a network of loudspeakers to reproduce the signal around the building. 

Alerting device power comes from the fire alarm’s standby battery, and is not reliant on building mains power, which may well fail during an emergency.

The alerting signals through a building must be identical. For modest additions to existing systems, it is permissible to retain the existing sound (siren, bell). Also on large sites where there is a uniform alerting signal, it is permissible for additional (new) systems to retain the same signal (even if it is, say, a bell sound), however a voice message must be provided on the new system.

EWIS Systems

A EWIS (Emergency Warning and Intercommunication System) is an enhanced system for fire alarm alerting and evacuation control in larger or more complex buildings. Instead of the whole building receiving the (evacuation) alerting signal simultaneously, the premises are instead subdivided into multiple evacuation zones. In response to signals from the fire alarm system, the EWIS system controls a zone-by-zone staged/phased evacuation according to a pre-programmed scheme. 

As with “all out” evacuation, the EWIS system generates the standard “rising whoop” evacuation signal and plays a voice message with evacuation instructions. With an EWIS these messages can be customized for various types of installations, and multi-lingual capabilities are usually available. In addition, a preliminary “Alert” tone, with separate verbal message, can be played to zones that have not (yet) reached the evacuation stage. In a high-rise, for example, this would typically mobilise evacuation (floor) wardens. 

A EWIS system is also designed to enable either the fire service or a designated building warden to take manual control of the evacuation, including directing Public Address (PA) messages to all or selected evacuation zones.

An (optional) Emergency Intercommunication (warden telephone) system allows building wardens or fire-fighting personnel to communicate with the master evacuation control panel to coordinate evacuation efforts. 

The rationale behind audio evacuation systems is, though conventional fire alarm notification devices alert occupants of a building to the presence of an emergency, they do not provide detailed information to the occupants, such as evacuation routes or instructions. Nor do they allow occupants in the greatest danger to have unimpeded access to escape routes. 

EWIS systems usually permit multiple messages. For instance, "non fire" messages can be programmed for situations such as a hazardous material spill, gas leaks, security breaches, etc. 

They can also be used to provide non-emergency building Public Address facilities.

Historically, the New Zealand Building Code Compliance Documents designated EWIS systems as “Type 8” Voice Evacuation Systems and they were mandated for new buildings primarily in healthcare, high-rise, and large crowd occupancies (cinemas, stadiums, shopping malls). This is no longer the case and such occupancies are now expected to be subject to specific fire engineering design. 

Under NZS 4512:2010, EWIS systems are required to comply with AS 2220 part 1: 1989 and to be installed to AS 1670.4: 2004.


The reliability of fire alarm systems is required to be much higher than some other building systems, due to the reliance placed on active fire protection systems for life safety. This is a fundamental consideration underpinning the NZ building Code and the associated Compliance Documents. Designs therefore tend to be conservative, based on risk and experience. 

Mains power supplies are expected to fail under fire conditions, so battery back-up is expected. Batteries are known to fail, so are tested almost continuously by the fire alarm system both for continued presence and capacity. Circuits are automatically supervised for fault conditions, producing fault signals in case of failure.
Sometimes wiring circuits are required to be installed with redundant paths. 

Because reliability is so important, monthly testing and annual surveying of fire detection and alarm systems by a qualified trade practitioner is mandatory. Fire detection systems are invariably listed on a building’s compliance schedule, and evidence of satisfactory test and survey must be submitted to the Territorial Local Authority before the building’s annual warrant of fitness (for continued occupation) can be issued.

“Types” of Fire Alarm Systems

The Compliance Documents for the New Zealand Building Code define several “types” of Fire Alarm systems. These are usually stated in Building Consents and are (very briefly) summarised as follows:

  • Type 1: – Domestic Smoke Alarms (not covered by NZS 4512: 2010)
  • Type 2: – A fire alarm system with manual call points, connected to the fire brigade.
  • Type 2f: – A fire alarm system with manual call points, not connected to the fire brigade.
  • Type 3b: – A suffix that designates a Type 4 or a Type 6 system is required instead wherever there is only a single escape route.
  • Type 3f: – A Type 3 fire detection and alarm system, not connected to the fire brigade.
  • Type 4: – A fire detection and alarm system with manual call points and smoke detectors, connected to the fire brigade. Heat detectors are allowed to replace smoke detectors in some locations. 
  • Type 4e: – A historical designation no longer used.
  • Type 4f: – A Type 4 fire detection and alarm system, not connected to the fire brigade.
  • Type 5: – A variation of a Type 4 for sleeping accommodation areas. Smoke detectors do not sound a general alarm or call the fire brigade, but instead sound a “hush”-able local alarm and alert building management. Heat detectors or sprinklers in the same areas sound a general alarm and call the fire brigade.
  • Type 6: – A fire sprinkler system connected to the fire brigade plus a Type 2 manual fire alarm system.
  • Type 6f: – A Type 6 fire sprinkler system plus manual fire alarm system, not connected to the fire brigade.
  • Type 7: – A fire sprinkler system connected to the fire brigade, plus a Type 4 or Type 4f fire detection and alarm system with smoke detectors and manual call points.
  • Type 7e: – A variation of a Type 7 that requires the Type 4 component to be a Type 5 within sleeping accommodation areas.
  • Type 7f: – A Type 7 fire sprinkler system plus Type 4 fire detection and alarm system, not connected to the fire brigade.
  • Type 8: – A historical designation for Emergency Warning and Intercommunication voice communication system (EWIS) and emergency telephone systems. No longer used.

For a fuller description, please consult the NZ Building Code Compliance Documents themselves, available for download here at MBIE website

Analogue Addressable Systems

“Conventional” fire detection and alarm systems are hard-wired to each group of detection devices. The control and indicating equipment is unable to distinguish alarm and fault conditions from individual devices within the group, and the actual alarm decision is made at each device. 

“Analogue Addressable” systems provide information about the exact location and status of every device at the control and indicating equipment. Furthermore, the alarm decision is generally made by the control equipment, rather than the detection device itself. 

In general, Analogue Addressable systems offer the following distinct advantages: 

  • Pre-alarm Indication – Incidents can be investigated, and possibly resolved, before the Fire Service is called. 
  • Maintenance Alert – dirty detectors can increase false alarms, but unnecessary cleaning wastes money. Maintenance alert facilities show which detectors need cleaning. 
  • Individual Detector Identification – each detector is uniquely identified. A full description of a detector’s precise location is displayed at the fire control panel, or on remote annunciators. This speeds the location of a fire or a fault. 
  • Wiring Faults – cut wires or short circuits on wiring do not generate false alarms, and are typically easier to locate. 
  • Adjustable Sensitivity – each detector can be tailored to its environment to give optimum sensitivity to fire phenomena and resistance to environmental influences or permitted activities (e.g. food preparation). 
  • Multi-Sensor Detectors – multi-sensor/multi-criteria detectors use sophisticated algorithms to make them less likely to generate a false alarm, but more likely to respond promptly to a real fire. 
  • Networking – analogue addressable systems typically have more comprehensive processing power and large site/campus-style multi-panel networking capabilities.

Overall, these technical advantages increase system performance and reduce unwanted building evacuations and calls to the Fire Service. Although analogue addressable systems can cost a little more initially, this can be recouped in reduced maintenance and false alarm costs, while offering the benefits of superior performance.

Unwanted (“False”) Alarms

Technology is improving all the time; however the false alarm rate from fire detection and alarm systems remains fairly constant – NZ Fire Service figures indicate that more than 90% of such calls are unwanted (“false”) alarms. With more and more systems being installed, the overall demand on Fire Service resources is increasing.

False alarms disrupt – business, staff, and customers. Repeated false alarms lead to complacency, and alarms being ignored. The Fire Service also levies callout charges for systems which repeatedly give unwanted alarms.

Correct detector selection and placement is of utmost importance in reducing false alarms. Other important measures are the control of building work, good building maintenance, regular detection system maintenance, and premises security

Domestic Smoke Alarms

Smoke Alarms are primarily used in domestic residential situations. They are different from the Smoke Detectors used in Fire Detection and Alarm Systems because they have a built-in alerting device, and are designed, tested, and manufactured to different standards. The most common examples are the battery-operated units available in many hardware stores. 

Early warning of the presence of smoke in a building is critical to life safety. Some fires can grow rapidly making escape very difficult, especially if the occupants are asleep, intoxicated, and/or the escape routes are smoke-logged. The time difference between escaping from a burning building or dying in a fire can often be measured in seconds. Sometimes fires can smoulder for hours, filling the premises with toxic fumes. Without the early warning provided by a smoke alarm, occupants can perish as they sleep without ever waking. 

“Type 1” Smoke Alarms are mandatory under the New Zealand Building Code Compliance Documents for new installations in domestic residential situations, including detached dwellings. Stand-alone battery-powered units are the minimum, however for optimal life-safety benefits, or larger dwellings, interconnected units are necessary to provide adequate sounder audibility to wake all occupants. Permanently-wired mains power, with long-life battery backup, is the most reliable configuration.

Because they have none of the inherent self-supervision or maintenance regimes of commercial Fire Detection and Alarm Systems, and they are not listed on a building’s compliance schedule for occupancy warrant of fitness, it is imperative that dwelling owners conduct their own regular maintenance and testing of their smoke alarms. 

These procedures include: annual cleaning with a vacuum cleaner (no disassembly), monthly testing with the alarm’s “test” button, and regular battery replacement (interval depends on type – annual for ordinary dry-cell batteries). 

A New Zealand Standard NZS 4514:2002 Interconnected Smoke Alarms for Single Household Units exists, however it is not mandatory. Under the current “Type 1” Compliance Document regime, the requirements are contained in section F7/AS1, and installation is required to be to AS 1670.6 and the manufacturer’s instructions.

Ionisation or Photoelectric? 

Commercially-available domestic smoke alarms are usually either ionisation chamber or photoelectric (light scattering) types. Considerable debate has taken place in the media as to which technology gives better performance, especially considering the price difference between the two is minimal (historically, photoelectric was considerably more expensive and drained batteries much faster). 

Ionisation smoke alarms respond most readily to the invisible products of combustion typical of fast flaming fires, but have a much slower response to smouldering fires. Escape routes can therefore become more smoke-logged before a warning is given. Ionisation detectors are prone to nuisance alarms from cooking activities, so must be sited well away from kitchens. They also contain a (very small) radioactive source, which in some countries presents environmental issues (not in New Zealand, where, under current legislation, they are permitted to be disposed of in the landfill with normal household rubbish). 

Photoelectric smoke alarms respond most readily to visible smoke, so can give a slower response to fast flaming fires with invisible products of combustion. They are also prone to nuisance alarms from steam, so must be sited well away from bathrooms and saunas. 

Photoelectric is the preferred smoke alarm technology for life safety in new installations, as it offers the most consistent early detection performance across all the likely fire scenarios in a residential environment.