How does the fire detection panel control mechanical smoke extraction?
The fire detection panel transmits a command order to smoke extraction equipment (extraction fans, dampers, smoke vents) as soon as detection is confirmed in a given zone. This transmission is done via dedicated dry contacts or through a communication bus connected to the smoke extraction control cabinet, according to the design provided by NBN S21-100-1.
The basic principle is zone division: each detection zone corresponds to a specific smoke extraction scenario, so that smoke is extracted as close as possible to its point of origin without depressurizing unaffected zones. This correspondence between detection zones and smoke extraction zones is defined at the design stage, in consultation between the design office, the installer and often the competent emergency zone (hulpverleningszone), which provides an opinion on the file before works begin.
What smoke extraction scenarios can the panel trigger?
A fire detection panel can control several distinct scenarios depending on the building configuration: local extraction from an affected zone, pressurization of a stairwell, shutdown of comfort ventilation in the affected sector, or a combination of several simultaneous actions. The choice depends on the building classification (low, medium or high) as defined by the Royal Decree of 7 July 1994.
| Scenario | Function | Zone concerned |
|---|---|---|
| Local extraction | Evacuate smoke from the affected room | Triggered detection zone |
| Stairwell pressurization | Maintain a usable evacuation route | Protected stairwell |
| General ventilation shutdown | Prevent propagation through ducts | Entire building or sector |
| Active compartmentation | Isolate the affected sector | Adjacent sectors |
Each scenario must be documented in the technical file submitted at handover, with details of the equipment activated and their sequence.
Why provide time delays between detection and smoke extraction?
A time delay is a period deliberately introduced between the detection of a fire start and the actual triggering of smoke extraction, intended to confirm the alarm or allow time for evacuation to begin without creating premature air flows. It differs from the general alarm delay, which follows its own logic.
In practice, a short time delay (in the order of a few tens of seconds) is used to confirm automatic detection before action on smoke extraction devices, to limit false triggers linked to transient phenomena (dust, steam). A longer time delay may be applied when the scenario first provides for evacuation of a zone before opening smoke vents, to prevent air flow from hindering occupant exit. These delays are set on a case-by-case basis in the study and validated during handover tests; they do not derive from a single generally imposed value.
What joint tests are required at building handover?
Joint tests consist of verifying, before commissioning, that each smoke extraction scenario triggers correctly from a simulated real detection in the corresponding zone, with measurement of time delays and verification of proper operation of each mechanical device. These tests cover the entire chain, from detection to actual opening of dampers or starting of fans.
The typical test reproduces, zone by zone, real detection (triggering of a detector or manual call point), then checks the smoke extraction response time, the activation order of equipment and the behavior of general ventilation. The result of each test is recorded in a handover report, submitted to the building owner and kept available for the emergency zone during its inspections. This document constitutes the reference for subsequent periodic inspections provided by NBN S21-100-2.
Who performs these tests and how often are they repeated?
Handover tests are performed by the installer, ideally BOSEC certified, in the presence of the building owner and, as appropriate, a representative of the emergency zone. The ANPI organization may also provide technical support on complex files.
After commissioning, the detection-smoke extraction coordination is not fixed: it must be rechecked during periodic maintenance operations defined by NBN S21-100-2, which sets inspection intervals for the detection installation and, by extension, the interfaces it controls. A joint functional test remains the only way to verify that smoke extraction still responds correctly after a building modification (partitioning, change of room use) or after an intervention on ventilation. The internal prevention advisor should request this test for any modification affecting either system.
What coordination errors are most commonly encountered?
The most frequent error is zone misalignment: a detection zone no longer corresponds exactly to the originally planned smoke extraction zone, often after reorganization of rooms or addition of a partition, without updating the technical file or conducting a new joint test.
Another classic error concerns electrical supply: detection and smoke extraction sometimes share the same backup source without sufficient redundancy, which cancels the benefit of time delay in case of common failure. Finally, the absence of real joint testing, replaced by separate tests of detection then smoke extraction without verification of their interaction, allows malfunctions to pass that only appear under real trigger conditions. These three points are the first checked during an inspection by the emergency zone or during a technical audit of the building.