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LEV testing - DSEAR and ATEX
When an extraction system handles flammable dust or vapour - wood dust, metal dust, solvent vapour - the system itself can contain an explosive atmosphere inside its ducts and collectors. That brings it under DSEAR and ATEX: the law on dangerous substances and explosive atmospheres. So the extraction has to be assessed and built to control not just the health risk but the explosion risk. Here is what that means, in plain terms. This is general information, not a substitute for a DSEAR assessment or specialist advice.
The short answer
Most extraction is thought of purely as a health-protection system - capturing dust, fume or vapour so people don't breathe it. But when the substance being extracted is flammable, the system takes on a second, serious dimension: the extraction itself can contain an explosive atmosphere. That brings a whole area of law and safety into play - DSEAR and ATEX. Here's what it means, in plain terms. This is general information, not a substitute for a DSEAR assessment or specialist advice. The hidden risk: an explosive atmosphere inside the system. When an extraction system handles a flammable dust or vapour, the inside of the system - the ductwork, the filters, the collector - can fill with a flammable mixture: a cloud of combustible dust in air, or a flammable vapour-air mixture. If that mixture is within its explosive range and meets an ignition source, it can explode. So the extraction system, by concentrating the flammable substance, can create an explosive atmosphere inside itself - a risk quite separate from the health risk it's there to control. Common examples of flammable extracted substances: wood dust, flour and other food dusts, many metal dusts (aluminium especially is highly flammable), and solvent and paint vapours (as in spraying). So a wood shop's dust extraction, a spray booth's vapour extraction, or a metal-grinding extraction can all involve this risk. DSEAR and ATEX: the law that applies. This explosion risk brings the extraction under DSEAR - the Dangerous Substances and Explosive Atmospheres Regulations 2002 - which is the law on preventing and controlling the risks from dangerous (including flammable) substances and explosive atmospheres. DSEAR requires, among other things, that the risks are assessed, that places where explosive atmospheres may occur are classified into hazardous zones and suitably protected and marked, and that ignition sources are controlled. Alongside DSEAR, ATEX requirements cover equipment used in explosive atmospheres (equipment has to be suitable - ATEX-rated - for the zone it's used in). So extraction serving a flammable substance falls squarely within this regime. The DSEAR assessment: finding and zoning the risk. A key step is the DSEAR assessment - a hazardous-area study. It identifies where explosive atmospheres can occur (including inside the extraction system and around it), and classifies those places into zones according to how likely and how persistent an explosive atmosphere is. Those zones are then marked and suitably protected, and they determine what equipment and controls are needed where. So the assessment is the foundation - it maps the explosion risk so it can be controlled. This is specialist work, needing competent assessment. Controlling ignition sources. A central part of explosion safety is keeping ignition sources out of the explosive atmosphere - because an explosive atmosphere only explodes if ignited. So the controls focus on eliminating potential ignition sources within the system and zones: electrostatic discharge (static can build up in extraction - especially with dusts - so filters and ductwork may need to be anti-static and properly earthed to stop static sparks); electrical ignition (any electrical equipment in the zones, including the fan and controls, must be suitable - this is where ATEX-rated equipment is required); hot surfaces (avoiding surfaces hot enough to ignite the atmosphere); and mechanical sparks (from friction or impact, for example a foreign object hitting a fan). So a big part of designing safe extraction for flammable substances is making sure nothing inside can ignite the atmosphere. Further explosion-protection measures. Depending on the assessment, further explosion-protection measures may be needed - because you can't always guarantee no ignition ever. These can include explosion venting (relief panels on a collector that safely release the pressure of an explosion in a safe direction), explosion suppression (systems that detect and suppress an explosion), and construction designed to contain or safely relieve an explosion. So the system may be built not only to prevent ignition but to survive or safely vent an explosion if one occurs. Which measures are needed depends on the DSEAR assessment. Health control still applies too. Importantly, all of this is in addition to the extraction's normal job of controlling the health risk. The system still has to capture the dust or vapour effectively to protect health (its LEV function), and still needs its normal thorough examination and testing under COSHH for that health-control role. So an extraction system serving a flammable substance has two overlapping requirements: it must control exposure (health, under COSHH, with LEV testing) and control the explosion risk (safety, under DSEAR/ATEX, with hazardous-area assessment and explosion protection). Both matter, and both must be maintained. The takeaway. So where extraction handles a flammable dust or vapour, the system itself can contain an explosive atmosphere, bringing it under DSEAR and ATEX. That means a hazardous-area assessment classifying the risk into zones, rigorous control of ignition sources (anti-static measures, ATEX-rated equipment, and more), and possibly explosion-protection measures like venting or suppression - all alongside the extraction's normal health-control function and its LEV testing. This is specialist territory needing a DSEAR assessment and competent design. This is general information, not a substitute for that. This is general information.
Key points
An explosive atmosphere inside the system
When an extraction system handles a flammable dust or vapour, the inside of the system - the ductwork, the filters, the collector - can fill with a flammable mixture: a cloud of combustible dust in air, or a flammable vapour-air mixture. If that mixture is within its explosive range and meets an ignition source, it can explode. So the extraction system, by drawing in and concentrating the flammable substance, can create an explosive atmosphere inside itself - a risk quite separate from the health risk it exists to control.
Common examples of flammable extracted substances: wood dust, flour and other food dusts, many metal dusts (aluminium especially is highly flammable), and solvent and paint vapours (as in spraying). So a wood shop's dust extraction, a spray booth's vapour extraction, or a metal-grinding extraction can all involve this risk. The point is that the very act of extracting a flammable substance - collecting it into ducts and a collector - concentrates it into potentially explosive conditions inside the equipment. This is why extraction for flammable substances is a special case, needing explosion safety, not just health control. So an explosive atmosphere inside the system - flammable dust or vapour concentrated in the ducts - is the core risk: the extraction can become an explosion hazard. The law that addresses it is next. So the system itself can hold an explosive mixture. This is general information. This is general information.
DSEAR and ATEX
This explosion risk brings the extraction under DSEAR - the Dangerous Substances and Explosive Atmospheres Regulations 2002 - the law on preventing and controlling the risks from dangerous (including flammable) substances and explosive atmospheres. DSEAR requires, among other things, that the risks from dangerous substances are assessed and eliminated or reduced, that places where explosive atmospheres may occur are classified into hazardous zones and suitably protected and marked, that ignition sources are controlled, and that measures are in place to deal with accidents and emergencies.
Alongside DSEAR, ATEX requirements cover equipment used in explosive atmospheres - equipment has to be suitable (ATEX-rated) for the zone it's used in, built to a protection concept that stops it igniting the atmosphere. So extraction serving a flammable substance falls squarely within this regime: the system, and the area around it where an explosive atmosphere can occur, has to be assessed, zoned, and fitted with suitable equipment and controls. This is a distinct legal framework from COSHH (which governs the health side) - both apply to extraction handling a flammable, hazardous substance. So DSEAR and ATEX - the law on explosive atmospheres - is the regime that applies: assess, zone, control ignition, use suitable equipment. The assessment that starts it is next. So DSEAR and ATEX govern the explosion risk. This is general information, not a substitute for a DSEAR assessment. This is general information.
The DSEAR assessment and zoning
A key step is the DSEAR assessment - a hazardous-area study. It identifies where explosive atmospheres can occur (including inside the extraction system and in the areas around it), and classifies those places into zones according to how likely and how persistent an explosive atmosphere is at each. Those zones are then marked and suitably protected, and they determine what equipment and controls are needed where (for instance, what rating of equipment is suitable in each zone).
So the assessment is the foundation of explosion safety: it maps the explosion risk so it can be controlled systematically, rather than guessed at. It tells you where the dangerous areas are, how dangerous, and therefore what precautions each needs. This is specialist work - identifying explosive atmospheres and zoning them correctly needs competent assessment (of the substances, their flammability, the concentrations, and the system), not a casual judgement. The DSEAR assessment for extraction sits alongside the COSHH assessment for the same system (which covers the health side) - both are needed for extraction handling a flammable, hazardous substance. So the DSEAR assessment and zoning - mapping where an explosion could occur - is the starting point: a competent hazardous-area study that classifies the risk. The controls it drives are next. So the assessment maps and zones the explosion risk. This is general information, not a DSEAR assessment. This is general information.
Controlling ignition sources
A central part of explosion safety is keeping ignition sources out of the explosive atmosphere - because an explosive atmosphere only explodes if it's ignited. So the controls focus on eliminating potential ignition sources within the system and the zones. Electrostatic discharge: static can build up in extraction, especially with dusts moving through ductwork, so filters and ductwork may need to be anti-static and properly earthed to stop static building up and sparking. Electrical ignition: any electrical equipment in the zones - including the fan, motors and controls - must be suitable for the zone, which is where ATEX-rated equipment is required (built not to ignite the atmosphere).
Other ignition sources to control include hot surfaces (avoiding surfaces hot enough to ignite the atmosphere - a concern with fans, motors and any heat), mechanical sparks (from friction or impact, for example a foreign metal object drawn in and striking a fan), and open flames or other hot work near the system. So a big part of designing safe extraction for a flammable substance is making sure nothing inside the system or its zones can ignite the explosive atmosphere. This is a rigorous, systematic exercise, guided by the DSEAR assessment. So controlling ignition sources - keeping ignition out of the explosive atmosphere - is the primary control: eliminate the sparks, hot surfaces and other ignition sources so the atmosphere can't be set off. In case ignition can't be wholly ruled out, further measures may be needed (next). So keep every ignition source out of the system. This is general information. This is general information.
Explosion protection and the health side
Depending on the DSEAR assessment, further explosion-protection measures may be needed - because you can't always guarantee no ignition ever occurs. These can include explosion venting (relief panels on a collector or duct that safely release the pressure of an explosion in a safe direction, so it doesn't burst the equipment dangerously), explosion suppression (systems that detect an incipient explosion and suppress it), and construction designed to contain or safely relieve an explosion. So the system may be built not only to prevent ignition but to survive or safely vent an explosion if one happens - which measures apply depends on the assessment.
Importantly, all of this explosion safety is in addition to the extraction's normal job of controlling the health risk. The system still has to capture the dust or vapour effectively to protect the people who'd otherwise breathe it (its LEV function), and still needs its normal thorough examination and testing under COSHH for that health-control role. So an extraction system serving a flammable substance has two overlapping requirements: control exposure (health, under COSHH, verified by LEV testing) and control the explosion risk (safety, under DSEAR/ATEX, via assessment, ignition control and explosion protection). Both matter and both must be maintained - the LEV testing we carry out addresses the health-control side, while the DSEAR/ATEX side is specialist explosion-safety territory. So explosion protection and the health side - venting or suppression, plus the LEV function - completes the picture: extraction for a flammable substance needs explosion safety designed in and its health-control function tested, together. So it's explosion safety plus health control, both maintained. This is general information, not a substitute for a DSEAR assessment or specialist advice. This is general information.
Questions
Because the system concentrates the flammable substance - the ductwork, filters and collector can fill with a combustible dust cloud or flammable vapour-air mixture, which if it meets an ignition source can explode; so the extraction creates an explosive atmosphere inside itself, separate from the health risk. Extraction of a flammable dust or vapour is an explosion risk because the system concentrates the flammable substance. When it handles a flammable dust or vapour, the inside of the system - the ductwork, filters and collector - can fill with a flammable mixture: a cloud of combustible dust in air, or a flammable vapour-air mixture. If that mixture is within its explosive range and meets an ignition source, it can explode. So by drawing in and concentrating the flammable substance, the extraction can create an explosive atmosphere inside itself - a risk quite separate from the health risk it exists to control. Common flammable extracted substances include wood dust, flour and other food dusts, many metal dusts (aluminium especially is highly flammable), and solvent and paint vapours. So a wood shop's dust extraction, a spray booth's vapour extraction, or a metal-grinding extraction can all carry this risk. The very act of extracting a flammable substance concentrates it into potentially explosive conditions inside the equipment. So it's a risk because the system fills with an explosive mixture. So because it concentrates flammable material into an explosive atmosphere. This is general information. This is general information.
DSEAR is the Dangerous Substances and Explosive Atmospheres Regulations 2002 - the law on flammable substances and explosive atmospheres; it applies to extraction handling a flammable substance, requiring the risk to be assessed, explosive-atmosphere areas classified into zones and protected, and ignition sources controlled. DSEAR is the Dangerous Substances and Explosive Atmospheres Regulations 2002 - the law on preventing and controlling the risks from dangerous (including flammable) substances and explosive atmospheres. It applies to extraction that handles a flammable substance because such a system can contain an explosive atmosphere (inside the ducts, filters and collector). Under DSEAR, the employer must: assess the risks from the dangerous substance and eliminate or reduce them; classify places where explosive atmospheres may occur into hazardous zones, which are then marked and suitably protected; control ignition sources; and have measures for accidents and emergencies. Alongside DSEAR, ATEX requirements cover equipment used in explosive atmospheres (equipment must be suitable, ATEX-rated, for its zone). So extraction serving a flammable substance falls within this regime, requiring a hazardous-area assessment, zoning, ignition control and suitable equipment. DSEAR is a distinct framework from COSHH (which covers the health side) - both apply to extraction handling a flammable, hazardous substance. So DSEAR governs the explosion risk of the extraction, requiring assessment, zoning and ignition control. So it's the explosive-atmospheres law, requiring assessment and zoning. This is general information, not a substitute for a DSEAR assessment. This is general information.
It's a study that identifies where explosive atmospheres can occur - including inside and around the extraction - and classifies those places into zones by how likely and persistent the explosive atmosphere is; the zones are marked and protected and determine what equipment and controls are needed, so it's the foundation of explosion safety. A hazardous-area assessment (part of the DSEAR assessment) is a study that identifies where explosive atmospheres can occur and classifies those places into zones. For extraction, it looks at where a flammable dust cloud or vapour-air mixture could form - including inside the extraction system and in the areas around it - and classifies those places into zones according to how likely and how persistent an explosive atmosphere is at each. Those zones are then marked and suitably protected, and they determine what equipment and controls are needed where (for example, what rating of equipment is suitable in each zone). So the assessment is the foundation of explosion safety: it maps the explosion risk systematically, telling you where the dangerous areas are, how dangerous, and therefore what precautions each needs - rather than leaving it to guesswork. This is specialist work: identifying and zoning explosive atmospheres correctly needs competent assessment of the substances, their flammability, the concentrations and the system. It sits alongside the COSHH assessment (for the health side) for the same extraction. So it's a study that maps and zones where an explosion could occur. So it identifies and classifies the explosion-risk areas. This is general information, not a DSEAR assessment. This is general information.
By eliminating potential sources within the system and zones - anti-static, earthed filters and ductwork to stop static sparks; ATEX-rated electrical equipment (including the fan) suitable for the zone; avoiding hot surfaces; and preventing mechanical sparks (like a foreign object striking the fan) - since an explosive atmosphere only explodes if ignited. Ignition sources are controlled in extraction systems by eliminating potential sources of ignition within the system and its hazardous zones - because an explosive atmosphere only explodes if it's ignited, so removing the ignition sources is central. The main ones to control: electrostatic discharge - static can build up in extraction, especially with dusts moving through ductwork, so filters and ductwork may need to be anti-static and properly earthed to stop static building up and sparking; electrical ignition - any electrical equipment in the zones, including the fan, motors and controls, must be suitable for the zone, which is where ATEX-rated equipment is required (built not to ignite the atmosphere); hot surfaces - avoiding surfaces hot enough to ignite the atmosphere (a concern with fans and motors); and mechanical sparks - from friction or impact, for example a foreign metal object drawn in and striking a fan. Open flames and hot work near the system are also controlled. So a big part of designing safe extraction for a flammable substance is ensuring nothing inside the system or its zones can ignite the atmosphere, guided by the DSEAR assessment. So control ignition by removing static, electrical, hot-surface and spark sources. So by eliminating every ignition source in the system. This is general information. This is general information.
Yes - DSEAR/ATEX covers the explosion risk, but the extraction still has its health-control job (capturing the dust or vapour so people don't breathe it), which is governed by COSHH and needs its normal thorough examination and testing; the two requirements sit alongside each other, both needing to be maintained. Yes - extraction covered by DSEAR still needs its normal LEV testing, because DSEAR and COSHH address different things. DSEAR (with ATEX) covers the explosion risk - making sure the flammable atmosphere the system can contain doesn't ignite and explode. But the extraction also has its normal health-control job: capturing the dust or vapour effectively so the people who'd otherwise breathe it are protected. That health-control function is governed by COSHH, which requires the LEV to be maintained and thoroughly examined and tested regularly (typically at least every fourteen months) to confirm it's still capturing the contaminant. So an extraction system serving a flammable, hazardous substance has two overlapping requirements: control the exposure (health, under COSHH, verified by LEV testing) and control the explosion risk (safety, under DSEAR/ATEX, via assessment, ignition control and explosion protection). Both matter, and both must be maintained - one doesn't replace the other. The LEV testing addresses the health-control side; the DSEAR/ATEX explosion safety is a separate, specialist matter. So yes - the health-control side still needs its LEV testing. So yes; COSHH still requires the LEV testing. This is general information. This is general information.
Yes - identifying and zoning explosive atmospheres, designing ignition control and any explosion-protection measures (venting, suppression), and selecting ATEX-rated equipment all need competent DSEAR/ATEX expertise; it's specialist territory, distinct from the health-control side, so get proper assessment and design rather than treating it casually. Yes - explosion safety for extraction handling a flammable substance is specialist territory. Several parts of it need competent, specialist expertise: identifying where explosive atmospheres can occur and classifying them into zones correctly (the hazardous-area assessment); designing the control of ignition sources (anti-static measures, earthing, selecting ATEX-rated equipment suitable for each zone); and determining and designing any further explosion-protection measures (such as explosion venting or suppression on collectors). Getting these right requires understanding of the substances' flammability, the concentrations, the system, and the DSEAR/ATEX requirements - it's not a casual judgement. This is distinct from the health-control side of the extraction (the LEV function, governed by COSHH and verified by LEV testing), which is a different expertise. So an extraction system serving a flammable substance needs both: competent explosion-safety assessment and design under DSEAR/ATEX, and the normal LEV testing for health control. The explosion-safety side in particular should be handled by those competent in DSEAR/ATEX, with a proper assessment - not treated casually or assumed. So yes - it's a specialist matter needing competent DSEAR/ATEX assessment and design. So yes; get proper specialist assessment and design. This is general information, not specialist advice. This is general information.
Extraction handling flammable dust or vapour must control an explosion risk under DSEAR/ATEX as well as the health risk under COSHH; we carry out the LEV thorough examination and testing for the health-control side, confirming the system captures the contaminant - with the DSEAR/ATEX explosion safety handled as the specialist matter it is. Ask us to test your LEV. This is general information.
