Smoke detector selection is set by the height of the space, the air movement and the value of the contents. The wrong choice means either a late alarm or three false alarms a week.
Three technologies
| Criterion | Point detector | Beam detector | Aspirating (VESDA type) |
|---|---|---|---|
| Operating principle | Optical or ionisation, single point | Transmitter-receiver beam | Draws air samples through a pipe network, measured by laser |
| Standard | EN 54-7 | EN 54-12 | EN 54-20 (classes A, B, C) |
| Typical ceiling height | Up to 10–12 m | 10–25 m | Unlimited (depends on pipe design) |
| Coverage | About 60–80 m² per detector | 100 m length × 14 m width | Up to 100–200 m² per pipe |
| Sensitivity | Standard | Standard | Very high (down to 0.005 percent obs/m) |
| Early warning | Once smoke reaches the ceiling | Once smoke breaks the beam | Before visible smoke |
| Sensitivity to air movement | High (dilution) | Moderate | Low (active draw) |
| Maintenance access | Physical access to every detector | Access to two end points | Central unit, accessible from floor level |
| Dirty or dusty environments | High false alarm risk | Lens contamination is a problem | Managed with filters |
| First cost | Lowest | Moderate | High |
| Maintenance cost | High (working at height) | Moderate | Low (from floor level) |
Which technology in which space?
| Space | Recommended | Reason |
|---|---|---|
| Office, hotel room, corridor | Point | Low ceiling, still air; the most economical |
| Shopping centre atrium | Beam | Large volume, point detectors hard to reach |
| High-bay warehouse | Beam or aspirating | Ceilings above 12 m; irregular air in narrow aisles |
| Automated warehouse (ASRS) | Aspirating | Narrow aisles, robot access, need for very early warning |
| Data centre / data hall | Aspirating | High air change dilutes smoke; point detectors respond late |
| Under a raised floor | Aspirating | Cable dense, hard to access, shallow volume |
| Cold store | Aspirating (heated unit) | Condensation disables point detectors |
| Historic building, museum | Aspirating | Minimal visual impact, pipework can be concealed |
| Dusty industrial production | Aspirating (filtered) or heat | False alarms are inevitable with point detectors |
The data centre rule: a data hall has 30 to 60 air changes per hour. That dilutes smoke starting inside a cabinet before it reaches the ceiling, and the fire grows while the point detector stays silent. The active draw of an aspirating system beats that dilution — which is why it is the industry's standard choice.
Design items in an aspirating system
- Pipe balance: each hole must draw approximately equal flow. On a long pipe the hole diameters are graded upwards, calculated in software.
- Transport time: the time from the furthest hole to the unit is limited by EN 54-20; the typical target is 60 to 90 seconds.
- Sensitivity class: Class A for very early warning (data centres), B moderate, C standard. The higher the class, the more false alarm management matters.
- Filter maintenance: in a dusty environment the filter change interval shortens, and that belongs in the operating budget.
- Staged alarms: Alert, Action, Fire 1 and Fire 2 thresholds are set separately. The first stage triggers human response and the last triggers suppression.
Field errors with beam detectors
- Structural movement. A steel roof expands with heat, the alignment between transmitter and receiver drifts and a fault alarm follows. Choose a product with automatic alignment.
- Obstruction in the beam path. A banner, light fitting or rack installed later breaks the beam. The beam route must be given to the operator in writing.
- The hot layer under the ceiling. In summer a hot layer forms under the ceiling and prevents smoke rising; the beam path must sit below that layer.
Turkish context
BYKHY references the EN 54 series for fire detection and requires the detection system to be connected to a monitored point. In practice point detectors are standard in residential, office and hotel buildings; beam detectors in shopping centre atria and high-bay warehouses; and aspirating systems in data centres, archives, museums and automated warehouses. Where the insurer requires it, an aspirating system is usually a precondition.
Frequently Asked Questions
Why are aspirating systems preferred in a data centre?
A data hall has 30 to 60 air changes an hour, which dilutes smoke starting inside a cabinet before it reaches the ceiling. The fire grows while a point detector stays silent; the active draw of an aspirating system beats that dilution.
Up to what ceiling height are beam detectors used?
Typically 10 to 25 m. Point detectors lose reliability above 10 to 12 m; in an aspirating system the height limit depends on the pipe design.
What is transport time in an aspirating system?
The time from the furthest sampling hole to the unit. EN 54-20 limits it, with a typical target of 60 to 90 seconds. As the pipe lengthens, the hole diameters are graded upwards to keep the balance.
Which detector suits a dusty production space?
False alarms are inevitable with point detectors. A filtered aspirating system, or heat detection instead of smoke, is preferred.
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Download MEP Calc on the App StoreThe EN 54 series (fire detection and alarm systems), in particular EN 54-7 (point smoke detectors), EN 54-12 (beam type) and EN 54-20 (aspirating). NFPA 72 National Fire Alarm and Signaling Code. BYKHY fire detection clauses. Values are for information only.