Return Air Plenums

The return air usually only has a short duct since they use the ceiling space as the plenum for the duct. This can cause big problems since most people do not consider the dust that has accumulated on the top of the ceiling tiles. This area can and will be contaminated with a cocktail of contributions from each occupant, from dead skin, body ash, tar, nicotine, dust, to their pets hair, and the particulates collected from their homes and workplaces.