Why is a cold storage warehouse particularly difficult to protect against fire?
A cold storage warehouse or cold room combines three constraints that rarely occur together elsewhere: constant sub-zero temperatures, a high relative humidity rate generating condensation and frost, and a building envelope made of sandwich panels whose insulating core (PIR or PUR foam) is combustible. Once ignited, these panels propagate fire very rapidly along walls and roofing, with significant release of toxic fumes. A detector designed for a temperate environment is simply not reliable in this context: its sensitivity drifts with cold, and its housing is not designed for condensing humidity. The installation design must therefore start from the actual ambient conditions of the premises, not from a standard solution.
What are the fire risks specific to a cold room?
The main risk in a cold room lies in the combustible nature of the sandwich panel insulation, combined with the presence of refrigeration units, electrical wiring and sometimes palletised loads of plastics or cardboard. Once started, a fire propagates inside the insulating structure itself, between the metal sheets, beyond the reach of conventional extinguishing means.
Technical ducts and false ceilings housing evaporators constitute frequent starting points, particularly in case of electrical faults linked to freezing or condensation on connections. Detection must therefore cover not only the storage volume, but also these technical spaces often difficult to access once the installation is in service.
Why do conventional smoke detectors not work in sub-zero environments?
A standard optical point detector is not designed to operate reliably below zero. The thermal shock when opening a door causes condensation, then frost, to appear directly on the detector's optical chamber, which causes false alarms or, conversely, masks actual smoke.
Cold also affects the electronics themselves: sensor sensitivity drifts, batteries and components lose reliability, and non-sealed housings crack with freeze-thaw cycles. A detector installed without particular precautions in a cold room ends up clogged with frost within a few weeks and becomes inoperative, without this being visible from the control panel.
Which detection technologies are suitable for sub-zero environments?
Two families of technical solutions meet cold constraints: certified low-temperature point detectors, whose housing and electronics are guaranteed by the manufacturer to operate at very low temperatures, and aspirating smoke detection (ASD), whose analysis sensor remains located outside the cold zone.
| Technology | Behaviour in sub-zero environment | Recommended use |
|---|---|---|
| Standard optical point detector | Sensitive to frost and condensation, sensitivity drift | To be avoided in cold rooms |
| Certified low-temperature point detector | Sealed housing, electronics guaranteed by manufacturer for cold | Small volumes, accessible storage areas |
| Aspirating detection with heated pipe | Sensor outside cold zone, air conveyed and heated before analysis | Large volumes, cold rooms, blast freezing tunnels |
| Linear barrier (flame or smoke detection) | Little sensitive to frost if optics clear, but requires regular defrosting | Large open volumes, significant height |
How does heated aspirating detection work?
Aspirating detection is based on a network of perforated pipes that continuously aspirate ambient air towards an analysis unit. In a cold room, the pipe section crossing the cold wall or ceiling is equipped with a heated section, which prevents the formation of condensation or frost inside the pipe before the air reaches the detector.
The unit itself is installed outside the cold zone, in a technical room at ambient temperature, which protects its electronics and facilitates maintenance without having to enter the cold room. This architecture allows large volumes to be covered with a reduced number of sampling points, a real advantage in a warehouse where each opening in the insulated wall must remain limited to preserve thermal performance.
Which Belgian regulations govern fire detection in a cold storage warehouse?
In Belgium, the design of a fire detection installation falls under standard NBN S 21-100-1, which sets the principles for detector design and installation, and its maintenance under NBN S 21-100-2. These standards do not provide specific rules for cold rooms, but their general principle, adapting the detector type to the actual ambient conditions of the premises, fully applies to this context.
The building classification according to the Royal Decree of 7 July 1994 (low, medium or high-rise building) determines the overall compartmentation and evacuation requirements within which detection is integrated. Installed equipment must be BOSEC certified, and ANPI may be consulted for complex cases. The Code on Well-being at Work (Book III, Title 3) also requires the operator to conduct a fire risk analysis that must integrate the specificities of its cold zones.
What specific maintenance does a detection system in a cold environment require?
A detection system installed in a cold room requires reinforced maintenance attention compared to a conventional installation, in addition to the periodic inspection required by NBN S 21-100-2. The technician must verify that the heated sections of the aspiration network are functioning correctly and that no frost accumulation has formed at sampling points.
Functional tests must include verification of the system's response under actual premises conditions, not only in temperate zones. The integrity of housings and cable passages crossing insulated walls must also be checked, as a sealing defect at this location creates a thermal bridge that precisely favours the condensation that the system is supposed to prevent.