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LEV testing - metalworking
The fine mist thrown off by CNC machines and metalworking is easy to dismiss as just coolant. It is a recognised cause of lung and skin disease - and the LEV that controls it is exactly what needs testing.
The short answer
Metalworking fluid - the coolant used in CNC machining, grinding and turning - is thrown into the air as a fine mist that workers breathe, and it is a recognised cause of occupational asthma, a serious lung condition called extrinsic allergic alveolitis, and skin disease. Where LEV controls that mist, it is subject to the same COSHH testing duty as any other LEV - and given how serious the harm is, testing that it actually works matters a great deal.
What coolant mist is
CNC machines, grinders and lathes flood the cutting area with metalworking fluid - coolant - to lubricate and cool the process. At the speeds involved, that fluid is thrown off and atomised into a fine mist and vapour that hangs in the air of the workshop, where it is easily breathed in and settles on skin. It is easy to think of it as harmless coolant; in health terms it is an airborne contaminant.
The mist is fine enough to reach deep into the lungs, and metalworking fluid can also become contaminated with bacteria as it is recirculated, adding a biological hazard to the chemical one. So what looks like a bit of coolant haze around a machine is actually a recognised occupational exposure - which is exactly why extraction to control it, and testing of that extraction, matters.
The harm
Metalworking fluid mist is linked to serious ill health. Breathing it is a recognised cause of occupational asthma and of extrinsic allergic alveolitis - also called hypersensitivity pneumonitis - a serious inflammatory lung condition that can develop from exposure to the mist, sometimes affecting groups of workers in the same shop. These are not minor complaints; they are conditions that can be disabling and, once established, may not fully reverse.
On the skin, contact with metalworking fluid is a common cause of occupational dermatitis. So the mist harms on two fronts - the lungs of those who breathe it and the skin of those who handle the work - which is why controlling it, and confirming the control works, is taken seriously in engineering and machining environments.
How LEV controls it
The control for coolant mist is local exhaust ventilation that captures it at source - extraction fitted to or around the machine, drawing the mist away before it reaches the operator's breathing zone. On modern CNC machines this often means enclosure with extraction; on open machines, hoods or capture points positioned to catch the mist thrown off during cutting. The aim is the same as any LEV: capture the contaminant where it is produced.
As with all LEV, that control only works if it is designed and maintained properly - the extraction has to reach the mist, pull it in effectively, and keep doing so as filters load and the system ages. A mist-extraction system that has degraded lets the coolant mist escape into the workshop air, exposing the operators it was meant to protect, often without any obvious sign.
Why it needs testing
Because metalworking fluid mist is a substance hazardous to health and LEV is the control, the extraction falls squarely under COSHH - which means it must be thoroughly examined and tested at least every 14 months, like any other LEV, and maintained in between. Testing confirms the mist extraction is actually capturing the mist and controlling exposure, rather than just running.
The stakes make that testing particularly worthwhile. Coolant-mist extraction can degrade invisibly, and a system that has quietly stopped controlling the mist is exposing workers to conditions that cause serious lung and skin disease. Given how invisible the mist and its degradation both are, measured testing is the only reliable way to know the control is working - and health surveillance often accompanies it, checking the workers as well as the extraction.
The takeaway
The message for any workshop running CNC, grinding or machining with metalworking fluid is that the coolant mist is a genuine health hazard, and the LEV controlling it is genuine LEV - subject to the COSHH testing duty and worth testing properly given the harm it guards against. Dismissing the mist as harmless coolant, and its extraction as something that does not need checking, is exactly the mistake that lets exposure go unnoticed.
So the coolant-mist extraction on your machines should be thoroughly examined and tested on the COSHH cycle, maintained between tests, and its performance confirmed by measurement - because occupational asthma, lung inflammation and dermatitis are what a failing system quietly causes. Testing the extraction is how you know it is still doing the job of protecting your operators' lungs and skin.
Questions
Yes. Metalworking fluid thrown into the air as a fine mist is a recognised cause of occupational asthma, a serious lung condition called extrinsic allergic alveolitis, and skin disease. It is an airborne health hazard, not just coolant haze.
Breathing it can cause occupational asthma and extrinsic allergic alveolitis - a serious inflammatory lung condition - and skin contact is a common cause of occupational dermatitis. The mist can also carry bacterial contamination.
With LEV that captures it at source - extraction fitted to or around the machine, often as enclosure with extraction on CNC or hoods on open machines - drawing the mist away before it reaches the operator's breathing zone.
Yes. As LEV controlling a substance hazardous to health, it falls under COSHH and must be thoroughly examined and tested at least every 14 months, and maintained in between - confirming it is actually capturing the mist.
Because coolant-mist extraction can degrade invisibly, and a system that has stopped controlling the mist exposes workers to conditions that cause serious lung and skin disease. Measured testing is the only reliable way to know the control still works.
Often, yes. Because the harm is serious and can develop from exposure, health surveillance frequently accompanies the LEV testing - checking the workers' health as well as confirming the extraction controls the mist.
We test metalworking-fluid mist extraction to COSHH and HSG258, confirming with measurement that it is still capturing the mist.
