Since I last posted, I've narrowed a few things down. One of the rooms that was affected (there were 2 rooms total), has been fixed. The french drain I installed around the perimeter of the front of the house, where water was creeping under the foundation, seems to have fixed the issue in the larger room. There is now no more musty smell in there. However, the other room, which is a "closet" that backs up directly to a bathroom, still has the odor, which has actually gotten worse. The smell is definitely partially sweet, and partially musty. I've cut the drywall all the way around the room to see if there is any signs of water damage, dead animals, etc inside of the walls. Interestingly enough, the inside of the walls that butt up to other rooms, smell fine. The walls that have concrete on the other side, have the odor present (perimeter walls). The only two things I haven't addressed yet are the roof (I'd have to cut the ceiling open because there is no attic access at this point for how low the roof pitches). The other thing would be the foundation (slab). I have fairly expensive laminate flooring and underlayment in that room, which would have to be removed, and the floor would have to be inspected for dampness. However, given the circumstances, it's been narrowed down quite a bit. The room has 4 walls (2 butt up to exterior concrete and 2 others butt up to interior rooms), a standard hollow core wood door, a West-facing window, and a drywall knockdown ceiling. There is only two piece of furniture in the room, which are bookcases. One is MDF (still wrapped in plastic to hold it together before I bolt it in), and the other is pine wood, also wrapped in thin plastic to protect it. I've just put two large shop fans, a big air purifier, an ionizer, and ozone generator all in the room with a big bucket of damprid (although humidity levels in that room are only 49% in south florida, which is fairly average). I've also sprayed half a can of lysol air spray into the room. I'll let you guys know how that works out, and hopefully we can figure it out. and ESMAN - let me know your notes as well. Thanks.

I would use the lime. Lime is not a toxic substance. It is used to treat sewage. Sewage Biosolids. Quicklime and calcium hydroxide (hydrated lime) have been used to treat biological organic wastes for more than 100 years. The treatment of human wastewater sludges (i.e., biosolids) by lime treatment is specifically prescribed in U.S. EPA regulations (40 C.F.R. 503). There are many examples of wastewater treatment systems using lime stabilization. How Lime Treatment Works--Lime treatment controls the environment needed for the growth of pathogens in biosolids and converts sludge into a usable product. Lime stabilization is a cost-effective option that generally has lower capital costs than alternative treatment options. The mechanism of lime treatment of biological wastes is based on several chemical reactions: Calcium hydroxide is an alkaline compound that can create pH levels as high as 12.4. At pH levels greater than 12, the cell membranes of harmful pathogens are destroyed. The high pH also provides a vector attraction barrier, preventing flies and other insects from infecting the treated biological waste. Because lime has low solubility in water, lime molecules persist in biosolids. This helps to maintain the pH above 12 and prevent regrowth of pathogens. When quicklime (CaO) is used, an exothermic reaction with water occurs. This heat release can increase the temperature of the biological waste to 70ºC, which provides effective pasteurization. The high pH also will precipitate most metals that are present in the waste and reduces their solubility and mobility. Lime will also react with phosphorus compounds. The solubility of calcium hydroxide also provides free calcium ions, which react and form complexes with odorous sulfur species such as hydrogen sulfide and organic mercaptans. Thus the biological waste odors are not >covered over= but actually destroyed. The addition of lime also increases the solids content of the waste, making it easier to handle and store.

Did anyone inspect the vent pipes to make sure they were installed correctly? Try also posting this on the Plumbing forum. I found this on another web discussion site: "It may be that you have a leak in the sewer stack, and that the expansion with the hot weather is whats causing it. Cold weather contracts various things and may seal it up again. I too am the type that I can smell things in parts per billion (reason why a lot of times, the Superintendent would ask me how the plant was doing, because I was the first to be able to detect things at the Waste Water Plant). Another possibility is that something is in your attic and its coming down through cracks in the ceiling or through the walls, in your bathroom, (dead squirrels or some critter). Now, make sure, to check your TRAPS in the shower or bath. its possible, that you have a plugged up soil stack, (though the plumber should have found this, if he checked the roof), and that when the temperature gets warm, or something happens outside, it sucks down the water from the traps in your bathrooms, (like when you use your sink in the kitchen and it creates a vacuum and draws down the water from the traps if the pipes aren't big enough...)"

Not much you can do since you have the brick unless you are willing to go for the $$$ and make repairs from the outside... In most cases, you fix everything on the outside to solve the problem on the exterior brick to prevent water intrusion and clean out and spray everything to prevent mold growth from the interior... patch and close up the wall.