Small question to get all you scientific guys thinking. - why is it when I empty the upstairs Hoover it's always full of fluff,while downstairs there's the usual grot but no fluff?
Is the upstairs carpet quite new and is it a wool blend, if yes then that's what creates the fluff.If the downstairs is a synthetic carpet then there wont be any fluff. This might explain it or you.
http://www.cavbrem.co.nz/carpet-care/carpet-traits.aspx#Fluffing