Air vents and their narrow openings are perfect dust catchers. Monthly vacuuming of these guys is pretty sufficient but once a year, take the time to remove the vent panel so you can thoroughly vacuum and wipe down the entire panel, inside and out. While that panel is off, run the vacuum cleaner attachment hose into the venting as far as you can to suck out any extra dust hiding out in there. - See more at: http://www.quickanddirtytips.com/house-home/housekeeping/14-places-where-dirt-hides-in-your-home#sthash.kqgkudm8.dpuf