Does a space under 300 m² need fire detection?Does a space under 300 m² need fire detection?

Does a space under 300 m² need fire detection?

No, there is no fixed surface threshold in Belgium, such as 300 m², that automatically triggers the obligation to install a fire detection system. This type of surface threshold exists in certain foreign regulations, but not in the Belgian framework. Here, the obligation stems from the building classification defined by the Royal Decree of 7 July 1994 establishing basic standards for fire and explosion prevention (low, medium or high buildings according to height), the purpose of the premises, the occupancy likely to be present, and the risk analysis required by the Code on Well-being at Work (Book III, Title 3). The surface area of an isolated space is therefore never, by itself, the criterion that settles the question.

What actually determines the obligation to install a fire detection system?

The obligation results from the combination of several criteria, never from a single surface figure. The first is the building classification according to its height: low building (less than 10 metres), medium (between 10 and 25 metres) or high (more than 25 metres), as defined by the Royal Decree of 7 July 1994. The second is the purpose of the premises: a production workshop, a storage depot or an office do not present the same risk. The third is the occupancy received, i.e. the number of people who may be simultaneously present in the space or building. The fourth is the result of the risk analysis that the employer must conduct, with the support of their prevention adviser, in accordance with the Code on Well-being at Work. It is this analysis, not a surface rule, that determines the necessary level of equipment.

How does occupancy influence the need for fire detection?

The occupancy refers to the number of people likely to occupy a space or building at any given time, including visitors and workers. The higher this occupancy, the longer the evacuation time required and the more critical early detection becomes to raise the alarm before exits become difficult to access. A 150 m² space hosting a large public (training room, company cafeteria) presents a different challenge from a storage space of the same area where only a few workers circulate. This is why the prevention adviser's risk analysis must consider actual occupancy and its mobility, not just square metres. This criterion often weighs more heavily than surface area in the decision to equip a space with automatic detection.

What role does the space's surface area play nonetheless?

Surface area is not the criterion that triggers the obligation, but it comes into play once the principle of equipment is established. It then serves to size the installation: number of detectors, division into detection zones, cable lengths and positioning of control devices, in accordance with standard NBN S21-100-1 relating to the design of fire detection installations. A large open-plan office will require more point or linear detectors than a small partitioned space, regardless of the regulatory threshold that motivated the installation. Surface area is therefore a technical design parameter, handled by the design office or BOSEC-certified installer, and not a parameter that determines the legal obligation itself.

Who decides, in practice, whether a space must be equipped?

The decision rests jointly with the operator, their prevention adviser and, depending on the case, the emergency zone (hulpverleningszone) responsible for the building's territory. The prevention adviser conducts the risk analysis required by the Code on Well-being at Work and identifies spaces with particular risk (storage of flammable products, boiler room, collective kitchen). The emergency zone provides an opinion during the processing of the environmental permit or planning permit, and may impose additional measures specific to the building concerned. The installer, approved and working with BOSEC-certified equipment, then translates these requirements into a technical solution compliant with standard NBN S21-100-1, before periodic maintenance is ensured according to standard NBN S21-100-2.

What happens for a small space located in a larger building?

A space is never analysed in isolation: it is the classification and risk level of the entire building that take precedence over the surface area of a particular room. An 80 m² space located on the third floor of a building classified as "high" according to the Royal Decree of 7 July 1994 is subject to the requirements of that building, regardless of its own surface area. Conversely, an isolated space of several hundred square metres in a low building with low occupancy may be subject to lighter requirements. Reasoning "my space is less than 300 m², so I am exempt" therefore has no basis in Belgian law: it is the building as a whole, its occupancy and its activity that set the applicable framework.