I've had the fortune (till recently) of growing in very dry environments. My standard set up was a 4x4 flowering area or a 4x4 tent, set up within a bedroom. An a/c in the window provides cooling (with the water catch tray cut out to prevent icing up in the winter) and your airflow is set up through fans.

Using high micron filtration (like 3M furnace filters) will remove most of the spores of PM from your grow environment. :)