Addressable vs conventional fire alarm: how to choose

In short

A conventional fire alarm shows which zone is in alarm. An addressable one shows which detector. That difference decides how fast people find the fire, how much of the building one damaged cable can switch off, and how much the system can tell you about its own condition. In the UK and in Russia the rules require an addressable system in some buildings. In Azerbaijan, the 2025 design code for high-rise buildings requires one. Where no rule decides for you, the choice comes down to the size of the building, who is inside and how the system will be maintained.

Conventional: the panel shows the zone

In a conventional system, detectors are wired in groups called zones. When a detector operates, the control panel reports only the zone, not the device. Someone has to walk the zone to find the fire.

BS 5839-1:2025, the UK code of practice for fire alarm systems, sets limits on zones in any system. In a conventional system they are all the location information you get:

• a person searching a zone should not have to walk more than 60 m to find the fire;
• a zone covers one storey only, unless the whole building is smaller than 300 m²;
• a zone is no larger than 2,000 m²; large open-plan areas with manual call points only may go up to 10,000 m²;
• a zone plan must hang next to every control panel and repeater panel, unless the panel has an equivalent display, such as a mimic diagram. The 2025 edition made this mandatory.

Addressable: the panel shows the device

In an addressable system, devices sit on a loop, and each one has its own number, its address. The panel reports the exact device that operated, in most systems with a text description of where it is.

Analogue addressable detectors go further: they send the panel a value that rises with smoke density. In Apollo's Discovery range, for example, 55 counts is the alarm level. On the XP95 ionization detector, values between 45 and 55 counts can serve as an early warning before the alarm. The detectors also compensate for dust building up in the chamber and can warn the panel that they need cleaning. These are features of the products, not requirements of a standard, and the scales differ between manufacturers.

How much one fault can switch off

A cable can be cut or short-circuited. The codes limit how much protection a single fault may take away:

• BS 5839-1:2025 (UK). Short-circuit isolators limit the effect of one fault to 2,000 m² and a single storey. Two faults at the same time should disable no more than 10,000 m², which caps one analogue loop at 10,000 m².
• SP 484.1311500.2020 (Russia), as amended from September 1, 2025. One fault in a signal or power line may cut off no more than 24 automatic detectors and one manual call point, and never automatic and manual devices at the same time.
• NFPA 72 (USA). A Class A pathway has a redundant path and keeps working after a single break. Class X also keeps working after a short circuit. Class B has no redundant path.

A short-circuit isolator disconnects only the faulty section of the loop. If not a single device may be lost to a short circuit, every detector needs its own isolating base.

When the rules require an addressable system

• United Kingdom. Where people need staff help to evacuate, as in care homes and hospitals, and the building has sleeping places for more than ten people, BS 5839-1:2025 says the system should be addressable.
• Russia. Appendix A of SP 484 requires an addressable system in, for example, hotels and dormitories from 2,000 m², apartment buildings taller than 28 m, shops from 3,500 m², schools from 3,000 m² and offices from 5,000 m². It is required regardless of size in any building where 50 or more people are present at once.
• Azerbaijan. AzDTN 2.7-9, the design code for high-rise buildings in force since September 30, 2025, says high-rise buildings "must be provided with an addressable fire alarm system". The code counts residential buildings 76–100 m tall and public buildings 55–200 m tall as high-rise. Addressable detectors go in every room except wet rooms, stairwells and vestibules.

Detectors and false alarms

In England in the year to March 2026, fire and rescue services attended 641,227 incidents, and 40% of them were fire false alarms. Of those false alarms, 172,247, about two-thirds, were caused by apparatus: an alarm or fire equipment operating in error. The leading causes were cooking and burnt toast (46,135), contaminants such as dust and steam (16,442), and testing (11,732). UK government guidance warns that where false alarms are frequent, people "may become complacent and not respond correctly to a warning of a real fire".

The right detector for each room is the first defense:

• In NIST tests of home smoke alarms, optical (photoelectric) alarms responded, often considerably, faster to smoldering fires, while ionization alarms responded somewhat better to flaming fires.
• Heat detectors suit smoky or dirty areas, such as a room used for cooking, but they respond only once a fire is well established.
• In tests by BRE, multi-sensor detectors detected test fires about as well as optical smoke detectors but reacted later to false alarm sources. Not all multi-sensors perform the same.

Maintenance

• Every week, someone on site operates a manual call point, a different one each time. If the system is connected to a monitoring station, warn the station before the test.
• A competent person inspects and services the system at least every six months. The UK Fire Industry Association says that without this, the system should no longer be considered compliant with BS 5839.

How to choose

1. Size and layout. Count the zones a conventional system would need under the limits above. The more zones, the more an addressable system saves on searching: it names the device.
2. People. If people sleep in the building or need help to evacuate, check whether the rules that apply require an addressable system.
3. Fault tolerance. Decide how much protection one damaged cable may take away. Loops with isolators limit it.
4. False alarm sources. List the kitchens, steam and dust in the building, and choose detectors for those rooms.
5. Local rules. Check which code applies. In Azerbaijan, a high-rise needs an addressable system.
6. Maintenance. Plan the weekly test and the six-monthly service before the system is handed over.

Common mistakes

• A smoke detector where cooking or steam will set it off. Cooking and contaminants caused more than a third of the apparatus false alarms in England.
• Testing without warning the monitoring station. Testing alone caused 11,732 false alarms in England in a year.
• Designing to outdated Russian figures. Since September 1, 2025, SP 484 has renamed the fire alarm zone (ZKSPS), dropped the cap of 32 detectors per zone and added the single-fault limit of 24 detectors.