Why not use a radioisotope and a metal plate, like in a smoke detector?
I think the element could be removed from the smoke detector and wired
into a different circuit that triggers on dust.
>
>I don't know how it works. For high particle counts (like your vacuum
>cleaner), I would guess you could use light scattering. I can't believe
>that would work at class 100 levels, though.
>
>-tony
>
>
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Received on Tue Jul 14 1998 - 10:01:36 BST