They look like they were from an industrial place, I work in a shipyard and our office is a portacabin style office inside the building hall and everything gets covered in that colour dust and I would guess that is what all ours look like inside.
I remember a few years ago when I used to work on photographic processing/printing equipment. I was sent to the Met police labs in south London because they were complaining of colour shifts in their prints.
The lab manager showed me what was happening and sure enough there was severe colour shift that seemed to happen over a period of time during the day. I think I spent about two days fiddling with this machine and getting nowhere. If anyone has done colour balancing then you'll know how tedious it is. On the third day I thought it must be an electronic fault, even though all the test points were reading correctly, so I went around the back of the machine and started sliding the PCB's out of the rack, I couldn't believe what I was met with, the dust was piled high across all the chips.
Out came the vacuum cleaner and after an hour all was working correctly. Bearing in mind this was supposed to be a clean lab I was amazed at the amount of dust electronic devices accumulate and the dust can be quite conductive in sensitive electronics.
Who remembers the archy sparkies in the old CRT tellies? That was caused by dust.
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