On 16/09/2019 23:30, alan_m wrote:

Having seen 3 examples in the last couple of days - why in films when
people are crawling around ventilation ducts they are always spotlessly
clean and when emerging those wearing black clothing show no signs of
any dust?


A bit like the soaps on TV where all the boiler suits worn always look
brand new and immaculate regardless of whether they have just serviced
the tractor/cat/mucked out the pigs etc.