By workplace & process
Metalworking fluid mist is hard to see and easy to breathe. Enclosure and extraction control it, and a test confirms they are doing the job.
The short answer
Metalworking fluid - the coolant that floods a CNC cutter, sometimes called white water - throws off a fine mist during machining. Breathed in, that mist can cause occupational asthma, hypersensitivity pneumonitis and, through skin contact, dermatitis. Because the fluids are complex, variable mixtures, there is no single workplace exposure limit for the mist; COSHH instead requires exposure to be controlled as low as reasonably practicable, which makes proving control through testing especially important.
The detail
The particles are small enough to be difficult to see under normal workshop lighting, so operators can be exposed without any obvious cloud. The fluid itself is a moving target: as it recirculates it picks up bacteria and endotoxin, its concentration and pH shift, and contamination changes what is actually in the mist. That is why HSE guidance pairs LEV with fluid quality management - regular checks on concentration, pH and bacterial contamination - rather than treating extraction as the whole answer.
The HSE has treated metalworking fluid as a priority, running inspection activity and releasing practical guidance on controlling mist during machining. The manufacturing sector already carries a higher-than-average rate of occupational asthma, and because the risk is known, employers are expected to control and monitor exposure whether or not harm has yet occurred. The HSE has published practical guidance and short films on controlling mist during machining, encouraging simple visual capture checks and real-time monitoring so operators can actually see whether the extraction is working rather than assuming it is. Health surveillance for skin and respiratory symptoms is a legal requirement under COSHH where workers are exposed, even when preventative controls are in place.
What it means for you
On a modern machining centre the primary control is usually enclosure - keeping the mist inside the machine - backed by extraction that removes it and a clearance period before the door is opened. An LEV thorough examination checks that the extraction is drawing mist away effectively, that the enclosure and ductwork are intact, and that airflow matches the commissioning benchmark, at least every fourteen months.
Common findings are extraction that has weakened through filter loading, doors opened before the mist has cleared, and compressed-air cleaning that re-launches settled fluid into the air. Getting the extraction tested, and running the machine with its clearance time respected, is what keeps a control that works on paper working in the cell.
The service behind the guide
We examine LEV on CNC and machining equipment against its ability to control coolant mist, and report on enclosure, airflow and any remedial work needed.
Questions
No single workplace exposure limit exists, because metalworking fluids are complex, variable mixtures. COSHH instead requires exposure to be controlled as low as reasonably practicable, so demonstrating control through testing matters.
Inhaled mist can cause occupational asthma and hypersensitivity pneumonitis, and skin contact can cause dermatitis. The mist is hard to see, and recirculating fluid can carry bacteria and endotoxin that change the hazard.
Where operators are exposed to mist, yes. The usual approach is to enclose the machine, extract the mist and allow a clearance period before opening the door, with the extraction tested under COSHH.
Yes. Under COSHH, health surveillance for skin and respiratory symptoms is required where workers are exposed to metalworking fluid mist, even when preventative controls are in place.
At least every fourteen months as a legal maximum, with fluid quality checks - concentration, pH and bacteria - carried out much more frequently as part of routine management.
Phoenix Duct Clean · by the numbers
We examine LEV on machining centres against how well it controls mist and give you a clear report. Call or email to book a visit.