What does "fire risk category" mean in the Code on Well-being at Work?
The Code on Well-being at Work (Book III, Title 3, fire prevention in the workplace) requires the employer to assess the fire risk specific to their activity and to classify workplaces according to this risk: low, medium or high. This classification is distinct from that of the Royal Decree of 7 July 1994, which ranks buildings into low, medium or high categories according to their height. The two logics coexist without being confused: one concerns the building itself, the other the activity taking place within it. A tertiary building classified as medium according to the 1994 Royal Decree may thus house offices at low risk and, in the same building, a maintenance workshop or server room at higher risk, each with its own detection and alarm equipment requirements.
What criteria determine the fire risk level of an activity?
The fire risk level is based on three families of criteria analysed jointly: the nature of the activity, the occupancy of the premises and the fire load. The nature of the activity examines the processes implemented (cold work, hot work, handling of flammable products, storage of combustible materials). Occupancy examines the number of people present, their mobility (able-bodied staff, bedridden patients, public unfamiliar with the premises) and the time schedule (daytime presence, night-time, continuous occupancy). The fire load examines the quantity of combustible materials present per area of premises. The prevention adviser combines these three families to arrive at a classification that directly determines the detection, alarm and extinguishing means to be provided in each zone of the building.
How does fire load influence risk classification?
Fire load refers to the amount of energy that would be released by the complete combustion of combustible materials present in a premises, relative to its area. The higher this load, the more rapidly a fire starting in that premises will develop and release significant thermal power, which directly affects the risk level assigned. An open-plan office with standard furniture and limited archives presents a moderate fire load. A warehouse storing plastic materials or a workshop using solvents presents a significantly higher fire load, even without permanent open flame. The analysis is not limited to listing the materials present: it takes into account their arrangement (storage at height or on the ground, clear or cluttered aisles) and their respective calorific value, as two premises of identical area may present very different risk levels depending on their actual contents.
What detection and alarm equipment is required according to the risk level?
The risk level assigned to each premises determines the sizing of detection, alarm and extinguishing means, without a single numerical threshold applying to all cases. A low risk (administrative offices, meeting rooms) calls for first-response means proportionate to rapid and uncomplicated evacuation, with detection targeted at sensitive areas. A medium or high risk (workshops, industrial kitchens, storage areas, patient rooms) generally calls for more extensive automatic detection, a more structured alarm organisation and sometimes automatic extinguishing. The design of these installations follows the zoning and detection logic described by standard NBN S21-100-1. The prevention adviser documents this reasoning in the risk analysis, which serves as a reference for the emergency zone (hulpverleningszone) when giving its opinion on the building file.
How does this reasoning apply according to the sector of activity?
The combination of the three criteria (activity, occupancy, fire load) produces very different risk profiles from one sector to another, even with comparable areas. The following table illustrates this logic without setting numerical thresholds, which remain specific to each risk analysis.
| Sector | Nature of activity | Typical occupancy | Fire load | Risk level tendency |
|---|---|---|---|---|
| Tertiary (offices) | Cold work, few flammable materials | Able-bodied staff, daytime presence | Moderate (furniture, archives) | Low to medium |
| Healthcare facility | Cold work, medical oxygen in certain areas | Patients with reduced mobility, continuous presence day and night | Variable according to departments | Medium to high depending on department |
| Industry (workshop, storage) | Hot work possible, solvents, storage of combustible materials | Trained staff, variable numbers | Often high depending on stored materials | Medium to high |
This classification remains indicative: each building must be subject to its own analysis, as the same sector may include premises with very different risks.
Who carries out the fire risk analysis and on what basis?
The company's prevention adviser carries out or coordinates the fire risk analysis, based on the requirements of the Code on Well-being at Work (Book III, Title 3) and on concrete knowledge of the building and its activities. This analysis appears in the company's fire prevention file and serves as a basis for the installer to size the detection system in accordance with NBN S21-100-1. The territorially competent emergency zone (hulpverleningszone) may be consulted for an opinion on this file, particularly when applying for a permit or making a significant change to the activity. The periodic inspection of the installation, carried out according to NBN S21-100-2, then verifies that the equipment in place remains consistent with the actual risk level, which must be reassessed if the activity, storage or occupancy of the premises changes.