Surface Preparation - I use wet sanding to reduce dust and particulates in the air that might contian lead and other harmful contaminants. Using wet-dry sanding sponges allows us to trap and dispose of these compounds harmlessly.
Course scraping and wire brushing is sometimes necessary, but I take every precaution to capture large pieces of old paint and debris. I put down plastic and vacuum to collect and dispose of this material. I control vacuuming in two ways. First, I use Heap internal filters. And second, I seal the vacuum against air leaks. These techniques are now mandated by the EPA under the new "Lead Safe Rules".
I want to acheive the best paintable surface possible without using harsh chemicals. These chemicals have sky-high VOC and odor levels. I use a very safe and effective product for washing - TSP. This cleanser works very well on a freshly sanded surface. Dry wiping removes any residue, and finalizes the surface for priming or painting.
Ventilation - Proper ventilation plays a large part in the capture of overspray. Air conditioning units, whole house fans and bath ventilation fans must never be used for intitial venting of active overspray. Venting out a window or door works best. When spraying indoors, I place plastic film on all surfaces not to be painted and dispose of it properly after any airborne spray has settled.
Application - I spray only when necessry. Hand painting helps to reduce paint use and airborne contaminants. It's a known fact that when spray painting only 65%-80% of the paint accurately hits its target. The rest collects on drop cloths and enters the air as paint dust.
Our brush and roll technique, on the other hand, is nearly 100% effective, and so reduces waste and airborne contaminants.
Aesthetics - In situations where a fine finish without brush marks is desired (such as kitchen and bath cabinetry, doors and casings, and sometimes large decorative moldings, spraying may be necessary. I take every precaution to capture overspray and airborne contaminants with platic barriors and drop cloths.