Furthermore, sensitive electronic instruments and parts accumulate deposits of oil mist and dust that can lead to malfunction, lost production uptime or greater strain on equipment such as lighting. Where this happens to heat exchange equipment, this can lead to higher power consumption and consequently higher costs. For certain processes, a heavy residue of mixed coolant and lubricant is deposited. This combination quickly clogs conventional filters, decreasing their lifetime and making maintenance much more difficult. Indoor air quality can experience long-term deterioration as oil accumulates in the ventilation system, and the environment becomes generally dirtier as oil on surfaces attracts dust and dirt.

Oil mist extraction equipment disposes of this coolant mist and smoke. The oil can be recovered and recycled, so that the cost of replacing it is avoided. High levels of filtration can be achieved with low-maintenance filter media. This provides an additional motivation to install specialised local exhaust ventilation for oil mist aside from reducing costs, improving the health and safety status of the facility and complying with regulations.

With both open and enclosed metalworking machines, oil smoke / mist extraction is usually done directly at the source, as this method is the most effective. For open machines, a hood or other structure is often installed to take in the oil mist or smoke and convey it to a filter unit through a duct. This improves extraction efficiency and lowers installation costs by eliminating ductwork and electrical connections. Enclosed machines have the air containing the oil sucked out of the space, and then conveyed to the filters as with a hood. Filtered air can be recirculated directly or sent to a heat exchanger.