The best thing is a good filter in the HVAC system. They have ratings on filters that can describe how small of a particulate can capture and including mold spores because mold spores basically a particulate. A filter with the equivalent of MERV 8 rating will capture particulate down as small as 3 microns. Most mold spores are 3 microns or higher. Aspergillus and Penicillium, for instance, are in the 3.3 micron range, stachybotrys is around 5 microns. So if you have at least a MERV 8 filtering furnace, you're going to be reducing the amount of mold spores that are in the air. It's not going to eliminate them but it'll be healthier.
If you're looking for the background particulate to the deterioration of the indoor environment there we recommend at least a MERV 10 filter because that will go down to 1 micron. And that will help filter out some of the background particulate as well. The problem that we see in Atlanta, there are no regulations of what kind of filters that the HVAC system should have. As a result, the vast majority of all of the places that we go into where they're having respiratory problems have this fiber glassy see through filters that are statistically equivalent to no filter at all when it comes to helping the indoor air quality. And it’s particularly true in apartment buildings, where we see that the filters are – they're useless in terms of filtering any of these kind materials out of the air.