Pungent Brick Walls

I own a small condo in the French Quarter of New Orleans. The downstairs closet has an old, exposed brick wall, which makes the condo smell like a cave. It's been checked for mold and that's not the problem. Is there some sort of a coating I can put on the wall to alleviate or at least lessen the smell? Also, I leave the air conditioning and a dehumidifier running all the time--good or bad idea?

A cave is cool and often damp, suggesting the odor that you described has something to do with moisture. The fact that it's not mold is good news. Warmth and moisture, two things New Orleans is famous for, are just what mold spores like.

Old, unsealed brick is porous, so it's capable of soaking up moisture and then releasing it as conditions become drier. Although sealing the brick might eliminate the odor you describe, it would be worth your while to take a closer look at the problem first.

Tracking Water to its Source
If the brick wall is producing a musty odor because it's perpetually damp, the question is--why? Moisture could be coming from either the inside or the outside of your condo. Exterior leaks could start with broken or missing gutters, gaps around door and window openings, or damaged siding--all the usual suspects. Take a careful look outside and see what you can find.

Water also can come from inside in the form of condensation. During the summer when your AC is running full-blast, interior walls are likely to be cooler than the air outside. When moisture-laden air sneaking through the walls of your house hits cool interior walls, water can condense.

Treating Your Condensation Problem
Air and vapor barriers are intended to slow this process down. In your climate, a vapor retarder would be applied to the outside of the exterior walls (it's just the opposite in the chilly north).

Installing vapor barriers after the fact isn't practical, but getting rid of moisture that accumulates inside the house can help. Using fans in the bathroom and the kitchen, along with making sure your clothes dryer is vented properly to the outside, are all steps that contribute to drier air.

Your dehumidifier and air conditioner should help you as well. I live in an area where air conditioning is optional, but we use a dehumidifier in our basement during the summer. When its reservoir fills up in a single day, we know humidity levels are very high. When the dehumidifier stops producing large amounts of water, we shut it off for the season.

The same common-sense test should tell you whether interior moisture is contributing to the problem you describe.

A Sealer Might Help, Too
If recurring moisture is not the problem and the old brick simply has absorbed a cave-like odor over the years, a sealer might indeed help.

Brick sealers that form a film on building exteriors (as opposed to water repellants, which don't) are generally discouraged by preservationists. Many brick sealers hold moisture in the wall, which often can lead to structural damage. That's obviously not a problem with an interior wall, and a sealer should stop or slow down any air exchange between your closet wall and the air inside your condo.

Finding a Sealer
A variety of water- and solvent-based sealers are on the market--silicones, urethanes, and acrylics among them. Sealers can be shiny, however--an unpleasant side affect outside but probably not an issue in a closet. I'd visit a store that specializes in masonry supplies and talk to an expert about which sealer would work best in your situation.

Before purchasing a sealer, dehumidifier, or anything else, find out if moisture is the real culprit.