Any dust, pet or insect dander that falls onto a carpet is trapped by the fibre ready to be vacuumed…

http://www.coit.com/spot-removal-guide

http://www.cleaningmag.com/news/view/bad-hygiene-risks-laid-bare/

http://www.icsmag.com/Articles/Feature_Article/0c1cbe4cd38de010VgnVCM100000f932a8c0____