What is the difference between an ATEX zone and a chemical room with fire risk?
An ATEX zone is a volume where a mixture of air and flammable gases, vapours or dusts can reach, during normal operation or in the event of malfunction, a concentration sufficient to explode. ATEX regulations (European directive transposed into Belgian law) then require certified equipment for zones 0, 1, 2 (gases and vapours) or 20, 21, 22 (dusts).
A laboratory or test room handling flammable solvents is not necessarily classified as ATEX: if the quantities used, the ventilation in place and the operating conditions prevent reaching the lower explosive limit, the room remains outside the ATEX zone. The remaining risk is then a risk of ignition of a liquid, vapour or material, i.e. a fire risk in the conventional sense, which falls under fire detection and not ATEX equipment. It is the risk analysis by the prevention adviser that determines this classification, room by room.
How does NBN S21-100-2 classify hazardous premises for non-explosive flammable substances?
The classification of premises according to their level of fire risk is first established during the design of the installation, based on NBN S21-100-1. It distinguishes premises with normal risk, where standard detection is sufficient, from premises with particular risk, where the presence of flammable vapours, combustible dusts or conditions favouring false alarms requires a specific detector and installation.
NBN S21-100-2, which governs the maintenance and periodic inspection of installations, uses this classification as a reference during maintenance visits: the technician verifies that the type of detector installed still corresponds to the actual use of the room, particularly if the activity of the laboratory or test room has evolved since commissioning. A room reclassified as particular risk after a process change (new solvents, new handling) must be subject to a reassessment of detection, not just a routine inspection.
Which detectors should be chosen for an environment laden with chemical vapours?
The choice of detector in a chemical laboratory must take into account both the risk of false alarms and the physical resistance of the equipment to aggressive vapours. Conventional optical smoke detectors are sensitive to aerosols and vapours present in the ambient air of a laboratory, which generates spurious triggering without actual fire.
Multi-criteria detectors (combining smoke, temperature and sometimes carbon monoxide) reduce this risk by cross-checking several signals before triggering the alarm. In areas where vapours are permanent but where the risk of open flame is well identified (test stations, solvent handling benches), a flame detector or thermal detector may prove more relevant than a smoke detector.
The housing itself must resist corrosion and chemical attack: treated housings, protection rating suitable for humidity and splashes, protected electronics. All installed equipment must remain BOSEC certified, guaranteeing that the detector has been tested and approved for fire detection use in Belgium, regardless of its enhanced resistance to vapours.
What other measures should be implemented in a chemical laboratory or test room?
Detection alone is not sufficient to control the fire risk of a laboratory handling flammable products: it must be coordinated with smoke extraction and, depending on the criticality of the equipment, automatic extinguishing. Properly sized mechanical ventilation limits the accumulation of vapours and contributes, alongside the ATEX question, to reducing the risk of widespread ignition in the event of fire outbreak.
For test rooms housing electronic equipment or costly process installations, an automatic gas extinguishing system is often preferred to water, as it does not damage equipment and acts quickly on an incipient fire in a confined environment. Smoke extraction, whether natural or mechanical, must be designed according to the building classification (low, medium or high) within the meaning of the Royal Decree of 7 July 1994, which sets the basic fire prevention standards applicable to the structure of the building housing the laboratory.
Who inspects and maintains fire detection in a chemical hazard laboratory?
The periodic inspection of the fire detection installation in a laboratory falls under NBN S21-100-2, which provides for preventive maintenance and inspection visits whose frequency is adapted to the type of installation and the risk level of the room. The company's prevention adviser remains responsible for reporting any change in activity likely to modify the room classification.
The emergency zone (hulpverleningszone) competent for the building's territory may be consulted for advice on the installation, particularly during a permit application or a significant change in operation, and it is this body that carries out on-site inspections. A laboratory that regularly changes products or processes should document these changes in its safety register, so that the installer can adjust the type of detector and room classification without waiting for the next periodic inspection.