Interesting that the HSE guidance on cutting fluids suggests that the fluids themselves be routinely monitored for bacterial levels rather than looking how far any mist has been spread https://www.hse.gov.uk/metalworking/bacterial.htm

This advice makes sense rather than trying to work out what the mist spreads might be.

You are not being asked to take part in some sort of research project are you?

Historically used dip slides when monitoring water based cutting fluids - has someone confused these with some form of tear strip?

Thanks for your comments, just as a summary reply to some of the comments:

I don't want to go back to the inspector until i know for sure its not a thing I should have known about and is used as an "industry standard" or similar measure somewhere in the Engineering industry. It doesn't look like it is from your comments. 

we've done smoke testing. I first tried it with a couple of smoke pencils inside the machine enclosures but there wasn't enough smoke for it to be visually revealing so I let off  a smoke bomb inside the enclosure to see how the air travelled. Both where inconclusive results insomuch as the medium didn't act like MWF mist does.

We banned the use of high pressure air guns on our machines over a year ago because of the increased risk of airborn contaminants. The operators either use vacuum cleaners or brush it off by hand.

We were giong to work in collaboration with the HSE on a methodology I "invented" whereby I mixed a UV flouescent die into the coolant (commonly used for leak detection) and then used UV Lighting to visualise the air contamination of MWF. It didn't work for me and the HSE were going to put thier considerable resources onto testing this method but reconed there was too much natural light for it to work in our factory so are not taking it forward with us. 

You are quite right, the MWF is not seen by the HSE as the probable cause and work they have done at other sites that have had outbreaks of COPDs, (Powertrain).  point the finger at the endotoxins that grow in the MWF itself. So we manage the MWF stringently on limiting bacterial and fungal growth. anyone interested in MWF management should go to the UKLA website for document tempates and methods for control along with a host of stuff on good MWF managment. Its the best I've seen and its free. 

Thanks again everyone, I'll leave the post open for a week or so before I take it down to see if someone has heard of this method. It was pretty much a shot in the dark to start with.