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LEV testing - warning signs
The extraction is on, humming away - but you can still smell solvent in the air. It's easy to assume that because the extraction is running, it's doing its job. But if you can smell the solvent, the vapour isn't being captured - and a running extraction that isn't capturing is a warning, not a reassurance. Here is what smelling solvents despite the extraction running means, and what to check. This is general information.
The short answer
The extraction's running, so the solvent vapour must be getting taken away - right? Not necessarily. If you can smell solvent in the air while the extraction is on, that smell is telling you something the running fan isn't: the vapour isn't being captured. Here's what it means, and what to check. This is general information. Running isn't the same as working. The core point is that a running extraction is not the same as a working one. The fan being on, the system humming, tells you it's running - but it tells you nothing about whether it's actually capturing the vapour at the source and removing it. Capture depends on the system genuinely drawing the vapour away where it's released, which can fail even while the fan runs. So you can't judge an extraction by whether it's on; you judge it by whether it's capturing - and the solvent smell is direct evidence about that. If the vapour were being captured at source, it wouldn't be reaching your nose in the room. So the smell means it isn't being captured (at least not fully). Why you can smell it: it's escaping. Solvent vapour is captured by drawing it away at the point it's released (from the solvent, the spraying, the process) before it spreads into the room. If you can smell it in the room, the vapour has escaped that capture and spread into the air you're breathing. So the smell is a marker of escaped, uncaptured vapour - which means the extraction isn't doing its core job of keeping the vapour out of the room air. (Smell is an imperfect measure - you can become used to a smell, and some hazards are harmful below the smell threshold - but a clear, persistent solvent smell is a definite sign of escaped vapour.) The possible causes. Why might the vapour be escaping despite the extraction running? Three main reasons. Poor capture at source: the extraction hood or capture point isn't positioned or designed to catch the vapour where it's released - too far away, wrong position, or a hood that doesn't enclose the source - so the vapour escapes into the room before it's drawn in. Capture depends on the hood being close to and over the source, not just the system running somewhere in the building. A degraded system: the extraction has weakened over time - a worn or failing fan, a blocked or leaking duct, a clogged filter - so it's no longer moving enough air to capture the vapour, even though it's still running and making noise. Degradation reduces capture silently: the fan still spins, but the airflow's dropped. Or the wrong extraction for the job: the system isn't suited to capturing a solvent vapour (which mixes readily with air and needs close capture right at the source, as it can't be captured by inertia like a heavier particle), or it's undersized for the amount of solvent or the task. So the smell could reflect a design/positioning problem, a degradation problem, or a suitability problem - all of which mean the vapour isn't captured. Why it matters: people are exposed. The important consequence is that the smell means people are being exposed to the solvent vapour. Solvents can harm health - many irritate the eyes, nose, throat and airways, and some cause more serious effects (some affect the nervous system, some are more toxic). So a persistent solvent smell despite the extraction running isn't a harmless nuisance; it's a sign that the control is failing and workers are breathing the vapour it's supposed to be capturing. The extraction being on can create false reassurance ('it's running, so we're protected'), which is exactly why the smell matters - it cuts through that false reassurance to show the control isn't working. What to check. So smelling solvent despite the extraction running should prompt checking, not shrugging. Check the capture at the source: is the hood or capture point positioned and close enough to catch the vapour where it's released? Check the system's performance: is it actually moving and capturing air, or just running (a fan can spin while the airflow's collapsed)? This is what a thorough examination and test measures - the actual capture and airflow, not just whether it's on. And check the extraction is suitable for capturing a solvent vapour and sized for the task. If the smell persists, the extraction needs investigating and testing, and the fault fixing - because until it's capturing the vapour, people are being exposed. So the smell is a prompt to have the extraction properly checked, not a thing to live with. The takeaway. So smelling solvents despite the extraction running means the vapour isn't being captured - a running extraction isn't a working one, and the smell is evidence it's failing to do its job. The cause may be poor capture at source, a degraded system, or the wrong extraction. Because the smell means people are being exposed to the vapour, it's a warning to act on - check the capture, test the system's performance, and fix the fault - not a nuisance to ignore because the fan is on. This is general information. This is general information.
Key points
Running isn't working
The core point is that a running extraction is not the same as a working one. The fan being on, the system humming, tells you it's running - but it tells you nothing about whether it's actually capturing the vapour at the source and removing it. Capture depends on the system genuinely drawing the vapour away where it's released, which can fail even while the fan runs.
So you can't judge an extraction by whether it's on; you judge it by whether it's capturing - and the solvent smell is direct evidence about that. If the vapour were being captured at source, it wouldn't be reaching your nose in the room, so the smell means it isn't being captured (at least not fully). This cuts through a common false reassurance: 'the extraction's running, so we're fine'. The smell shows that running isn't the same as protecting. Smell is an imperfect gauge (you can get used to a smell, and some hazards harm below the smell threshold), but a clear, persistent solvent smell is a definite sign of escaped vapour. So running isn't working - a fan on the wall proves nothing - is the key insight: judge the extraction by capture, not by whether it's on, and the smell reports on the capture. Why you smell it is next. So a running fan doesn't mean captured vapour. This is general information. This is general information.
You smell it because it's escaping
Solvent vapour is captured by drawing it away at the point it's released - from the solvent, the spraying, the process - before it spreads into the room. If you can smell it in the room, the vapour has escaped that capture and spread into the air you're breathing. So the smell is a marker of escaped, uncaptured vapour: it's got past the extraction and into the room, which is exactly what the extraction is supposed to prevent.
This is why the smell is meaningful: it's not a random odour but a direct indication that the vapour is where it shouldn't be (in the breathing air) rather than where it should be (captured and removed). The extraction's core job is to keep the vapour out of the room air, and the smell shows it's failing at that. The stronger and more persistent the smell, the more vapour is escaping. So the smell isn't a cosmetic issue - it reflects a real failure of capture, with the escaped vapour being breathed. Why it's escaping (the causes) is next. So you smell it because it's escaping - the vapour has reached the room air - is the interpretation: the smell means uncaptured vapour in the breathing air. So the smell marks escaped, breathable vapour. This is general information. This is general information.
The possible causes
Why might the vapour be escaping despite the extraction running? Three main reasons. Poor capture at source: the extraction hood or capture point isn't positioned or designed to catch the vapour where it's released - too far away, wrong position, or a hood that doesn't enclose the source - so the vapour escapes into the room before it's drawn in. Capture depends on the hood being close to and over the source (covered in the hood-and-capture-point-design page), not just the system running somewhere in the building.
A degraded system: the extraction has weakened over time - a worn or failing fan, a blocked or leaking duct, a clogged filter - so it's no longer moving enough air to capture the vapour, even though it's still running and making noise. Degradation reduces capture silently: the fan still spins, but the airflow's dropped (as covered in the why-a-working-fan-doesnt-mean-a-working-lev-system page). Or the wrong extraction for the job: the system isn't suited to capturing a solvent vapour (which mixes readily with air and needs close source capture, since it can't be captured by inertia like a heavier particle), or it's undersized for the amount of solvent or the task. So the smell could reflect a positioning problem, a degradation problem, or a suitability problem - all meaning the vapour isn't captured. So the possible causes - poor capture, degradation, or wrong extraction - are what to investigate: the reason the running extraction isn't capturing. Why it matters is next. So it's poor capture, a degraded system, or the wrong kit. This is general information. This is general information.
It means people are exposed
The important consequence is that the smell means people are being exposed to the solvent vapour. Solvents can harm health - many irritate the eyes, nose, throat and airways, and some cause more serious effects (some affect the nervous system, some are more toxic than others). So a persistent solvent smell despite the extraction running isn't a harmless nuisance; it's a sign that the control is failing and workers are breathing the vapour it's supposed to be capturing.
The extraction being on can create false reassurance - 'it's running, so we're protected' - which is exactly why the smell matters: it cuts through that false reassurance to show the control isn't actually working. A workplace that trusts the running extraction and ignores the smell is leaving its workers exposed while believing they're protected, which is worse than knowing the extraction is off. So the smell should be treated as the useful warning it is - evidence of an exposure the running fan is masking. This links to the broader point that an extraction's real job is capture, not running, and that you can't rely on it being on as proof it's working. So it means people are exposed - the smell cuts through false reassurance - is why it matters: the smell reveals an exposure the running extraction hides. What to check is next. So the smell reveals a real, hidden exposure. This is general information. This is general information.
What to check
So smelling solvent despite the extraction running should prompt checking, not shrugging. Check the capture at the source: is the hood or capture point positioned and close enough to catch the vapour where it's released, or is it too far away or badly placed? Check the system's performance: is it actually moving and capturing air, or just running (a fan can spin while the airflow's collapsed through a blockage, leak or worn fan)? And check the extraction is suitable for capturing a solvent vapour and sized for the task and the amount of solvent.
Crucially, the performance check is what a thorough examination and test measures - the actual capture and airflow, not just whether the system is on. So the reliable way to find out why the vapour is escaping is to have the extraction properly tested, which reveals whether it's capturing and where it's failing (a degraded fan, a poor hood, a blocked duct). If the smell persists, the extraction needs investigating and testing, and the fault fixing - because until it's capturing the vapour, people are being exposed. So the smell is a prompt to have the extraction properly checked and tested, not a thing to live with. So what to check - capture, performance, and suitability, tested - is the action: examine the capture, test the actual performance, confirm suitability, and fix what's failing. So check and test it, don't ignore the smell. This is general information. This is general information.
Questions
It means the extraction isn't capturing the vapour - if it were drawn away at source, you wouldn't smell it in the room; a running extraction isn't a working one, so the smell is evidence the vapour is escaping into the air people breathe, whatever the fan is doing. If you can smell solvent while the extraction is running, it means the extraction isn't capturing the vapour. Solvent vapour is supposed to be drawn away at the point it's released, before it spreads into the room - so if you can smell it in the room, the vapour has escaped that capture and reached the air you're breathing. The key point is that a running extraction is not the same as a working one: the fan being on tells you it's running, but not whether it's actually capturing the vapour. The smell is direct evidence about the capture - if the vapour were being captured at source, it wouldn't reach your nose in the room. So the smell means it isn't being captured (at least not fully), whatever the fan is doing. This cuts through the false reassurance that 'the extraction's running, so we're fine'. The causes could be poor capture at the source (bad hood position), a degraded system (weak fan, blocked duct), or the wrong extraction for the job. Whatever the cause, the smell means people are being exposed to the vapour. So it's a warning the extraction is failing, to check - not a nuisance to ignore. So it means the vapour is escaping and isn't being captured. This is general information. This is general information.
Because a running extraction isn't necessarily capturing - the fan can be on while the vapour escapes at source (poor hood position) or while the airflow has collapsed (a degraded fan, blocked duct); capture depends on drawing the vapour away where it's released, which can fail even as the fan runs. You can smell it despite the extraction being on because a running extraction isn't necessarily a capturing one. The fan running tells you the system is powered and turning, but capture depends on the system actually drawing the vapour away at the point it's released - and that can fail even while the fan runs. Two common ways this happens. First, poor capture at source: if the extraction hood or capture point isn't positioned close to and over where the vapour is released, the vapour escapes into the room before it's drawn in - the system is running, but not catching the vapour at source. Second, a degraded system: over time the extraction can weaken (a worn or failing fan, a blocked or leaking duct, a clogged filter) so it's no longer moving enough air to capture, even though the fan still spins and makes noise - the airflow has dropped while the fan runs on. Either way, the vapour escapes and you smell it, despite the extraction being on. This is why you can't judge an extraction by whether it's running - you judge it by whether it's capturing, which the smell reports on. So because running doesn't guarantee capture - the vapour escapes anyway. So because the fan runs but isn't capturing the vapour. This is general information. This is general information.
Yes - the smell means the vapour has escaped into the air people breathe, so they're being exposed; solvents can irritate the airways and some cause more serious effects, so a persistent smell despite extraction is a sign the control is failing and workers are breathing the vapour, not a harmless nuisance. Yes - a persistent solvent smell means people are being exposed to the vapour. The smell exists because the vapour has escaped the extraction and spread into the room air - the air people are breathing - so they're inhaling the solvent vapour that the extraction is supposed to be capturing and removing. This matters because solvents can harm health: many irritate the eyes, nose, throat and airways, and some cause more serious effects (some affect the nervous system, some are more toxic). So a persistent solvent smell despite the extraction running isn't a harmless nuisance - it's a sign the control is failing and workers are being exposed to a substance that can harm them. The danger is that the running extraction creates false reassurance ('it's on, so we're protected'), which can lead people to ignore the smell and accept the exposure. But the smell is precisely the warning that cuts through that false reassurance, revealing the hidden exposure. So a solvent smell should be taken as evidence of a real exposure to act on, not tolerated. That said, the absence of a strong smell doesn't guarantee safety (you can get used to a smell, and some hazards harm below the smell threshold), so control shouldn't rely on smell - but a clear smell is a definite warning. So yes - the smell means exposure, and it's a warning to act on. So yes; the escaped vapour is being breathed. This is general information. This is general information.
Check the capture at the source (is the hood close and positioned to catch the vapour), the system's actual performance (is it moving and capturing air, or just running - a fan can spin while airflow has collapsed), and whether the extraction suits capturing a solvent vapour and is sized for the task - a thorough test measures the real capture. If you smell solvent despite the extraction running, check three things. The capture at the source: is the extraction hood or capture point positioned and close enough to catch the vapour where it's released, or is it too far away or badly placed to catch it before it escapes? The system's actual performance: is it really moving and capturing air, or just running? A fan can spin and hum while the airflow has collapsed through a blockage, a leak, or a worn fan - so 'it's running' doesn't prove it's capturing. And the suitability: is the extraction suited to capturing a solvent vapour (which needs close source capture) and sized for the task and the amount of solvent? Crucially, the performance check is what a thorough examination and test measures - the actual capture and airflow, not just whether the system is on - so the reliable way to find out why the vapour is escaping is to have the extraction properly tested, which reveals whether it's capturing and where it's failing. If the smell persists, the extraction needs investigating, testing, and the fault fixing, because until it captures the vapour, people are exposed. So check the capture, test the real performance, confirm suitability, and fix the fault. So check capture, test performance, and confirm it suits the job. This is general information. This is general information.
No - a running extraction isn't necessarily a working one; the fan being on doesn't prove it's capturing the vapour, which can fail through poor hood position or a degraded system while the fan still spins, so judge it by whether it captures (the smell being one sign), not by whether it's on. No - you can't trust the extraction just because it's running. A running extraction is not the same as a working one: the fan being on tells you the system is powered and turning, but it tells you nothing about whether it's actually capturing the vapour at source and removing it. Capture can fail even while the fan runs - through poor capture at source (a hood too far from or badly positioned relative to where the vapour is released, so the vapour escapes before it's drawn in) or through a degraded system (a worn or failing fan, a blocked or leaking duct, a clogged filter reducing the airflow while the fan still spins and makes noise). So the sound of the fan is no proof the vapour is being captured. This is exactly why a solvent smell despite the extraction running matters - it's evidence that the running system isn't capturing, cutting through the false reassurance of the fan being on. You judge an extraction by whether it's capturing the contaminant, not by whether it's switched on - and the reliable way to know is to have it tested (which measures the actual capture and airflow), not to trust that it's running. So relying on the extraction being on is a mistake; confirm it's capturing. So no - running isn't the same as working; check that it captures. This is general information. This is general information.
A clear, persistent solvent smell is a definite sign of escaped vapour, but smell is imperfect - you can get used to a smell, and some hazards harm below the smell threshold - so the absence of smell doesn't prove safety; use the smell as a warning to act on, but don't rely on smell alone to judge the control. A clear, persistent solvent smell is a definite and reliable warning of escaped vapour - if you can smell it, the vapour has got past the extraction into the room air, so it's real evidence the control is failing and worth acting on. So a solvent smell should always be taken seriously as a warning. However, smell is not a perfectly reliable measure of exposure in general, for two reasons. First, you can become used to (desensitised to) a smell over time, so a workplace where the smell is constant may stop noticing it, even though the exposure continues - the absence of a noticed smell doesn't mean the vapour has gone. Second, some hazards can be harmful at concentrations below the level at which you'd smell them, so 'I can't smell anything' doesn't guarantee the air is safe. So the smell is a useful warning when present (a clear smell means escaped vapour, act on it), but its absence isn't proof of safety, and control shouldn't rely on smell alone. The reliable way to judge whether the extraction is capturing is to have it properly tested (measuring the actual capture and airflow), rather than relying on whether anyone can smell the solvent. So a smell is a good warning to act on, but not a substitute for testing. So a clear smell is a real warning, but no smell isn't proof of safety. This is general information. This is general information.
Smelling solvent while the extraction runs means the vapour isn't being captured - a running system isn't a working one; we thoroughly examine and test LEV, measuring whether it actually captures the vapour and finding where it's failing, so a running-but-not-working system is caught and fixed, not trusted. Ask us to test your LEV. This is general information.
