Oil Mist vs. Oil Smoke

Oil mist and oil smoke are formed in industrial environments where CNC grinding, forging, heat treating systems, die casting, and other machining processes take place.

The contamination that develops from these machine processes does not consist of only oil mist or oil smoke, but is generally made up of both. However, when the droplets are larger (up to 20 microns) it's considered to be oil mist and when they are smaller (under 1 micron), oil smoke.

What's the Difference Between Oil Mist & Oil Smoke?

Oil Mist

Oil mist is a made up of colloidal particles, or droplets, that are dispersed when oil-based lubricants are used for cooling, lubricating, or chip removal during machining of metal and certain plastic components, or where milling, drilling, grinding and turning happen.

For measure, oil mist droplets are the same size as bacteria and range between 1-10 µm. The current OSHA standard for mineral oil mist is 5mg of mineral oil mist per cubic meter of air averaged over an 8-hour work shift and 15 mg/m3 TWA (total particulate).

Oil Smoke

Oil smoke may sometimes have a blue-like color and is composed of the same droplets as mist. The main difference between the two is that oil smoke particles are smaller and normally materialize into more substantial amounts.

Oil mist is produced when machines are working at high speeds, when using high coolant pressures, during MQL (minimum quantity lubrication), in hot manufacturing processes, in facilities where food is being processed, or in certain rubber and plastic applications.

Also measured in mg/m3, the size of oil smoke particles range between 0,1–1 µm.