Chris Bacon wrote...
The last really nasty belt I received was a static shock when I foolishly
put my hand in a Dyson vacuum cleaner canister to dislodge the fluff

How did that happen, then?

Basically works like a van der Graaf generator. Dry dust particles build up
a static charge by tribo-electrification and this gets transfered to the
walls of the container. Static charge is always repelled towards the
outside of a container and because the dust-container is made of insulating
plastic it builds up on the inside surface of the cylinder. As soon as an
eathed paw is inserted a path to earth is provided and you are on the
receiving end of a large and painful spark!

Used to have the same problem with a HEPA filtered Nilfisk vacuum cleaner
that I used to clean up contaminated spillages of dry alumina powder from an
air abrasive machining apparatus (precision "sand-blaster" I used for
preparing semiconductor specimens). The static charge on the vacuum pipe
(and hence me) - of opposite polarity to that on the dust - would build up
until whatever was most insulating in the circuit via me to ground broke
down, whereupon I would get a nasty shock - until I made up an earthing
strap for the vacuum cleaner!

David