Mold put South Carolina's first family out of the Governor's Mansion this summer. Gov. Mark Sanford and his family decamped to the beach while workers are cleaning mold out of the air conditioning at the residence in Columbia.

Pervasive and persistent, mold is everywhere, from elegant mansions to humble homes. Usually, it begins with a chink in the armor that keeps water in its place. A broken pipe, a leaky roof, a crack in windows or siding. Even a flood that swamps the place.

When water gets in, mold runs amok.

How do we know?

"You usually know if you can see it or smell it. It's pretty simple," says Kathi Giaramita, of ServiceMaster, a national cleaning and disaster recovery company with franchises in the Carolinas.

Sometimes you will both see and smell it: a slimy or dusty black, pink or green mold and its distinctive musty odor.

Other times, you smell it, but don't see it, a clue the mold is behind the wall or above the ceiling.

And other times, you see it but don't smell it, a signal the mold is there, but not growing due to the absence of water.

Water or excessively high humidity indoors for two to four days are what makes mold grow, say experts such as Giaramita and Romie Herring, industrial hygiene consultant supervisor for the N.C. Department of Health and Human Services.

Herring says there are at least 100,000 species of mold in the world.

Giaramita says, "Mold needs three things to grow -- indoors or out. The spores are present everywhere in our environment, they come inside with us."

They need organic matter -- something living now or once alive, such as cut wood -- on which to feed. Lastly, they require moisture, which doesn't have to be standing water, though it often is, caused by dripping pipes or even tiny chinks in the roof. Herring points out that flood waters present an especially fruitful opportunity for mold to grow in homes.

That's because it's dirty and has time to soak into wood, walls and floors. This leaves behind a rich banquet for mold spores, one that requires professional help.

Excessively high humidity can also spur mold growth, often in crawl spaces, the space between walls, basements and garages.

It wasn't a hole in the roof or a break in the pipes that caused mold problems at the Governor's Mansion in Columbia, prompting Gov. Sanford's family to move out in June.

The mold named stachybotrys was found on the inside of the mansion's air-handling system. The Sanford family left the house for Sullivan's Island while the system is being disassembled and cleaned, a job expected to take until early September.

Before school starts for the Sanford children later this month, the family expects to live in the mansion's pool house: two rooms and a galley kitchen.

Extensive renovation at the mansion four years ago allowed mold to grow in the air conditioning. Dust from cutting drywall and sawing and sanding of wood blew into the system's ductwork and air handlers, providing a rich source of nutrients for spores to develop mold. Jenny Sanford, the governor's wife, said she, members of the mansion staff, and the four Sanford children had all suffered respiratory ailments and other symptoms.

Experts say mold can cause allergic reactions, and Herring says these can be serious in people with compromised immune systems.

Giaramita says mold is a well-documented allergen. However, regulatory agencies haven't declared it hazardous. "But that is not to say it is safe to have growing in homes."

Herring says prevention is the key to keeping mold from becoming a problem in homes.

"Just keep an eye on what's going on. Take care of maintenance. Fix those leaks. Keeping the building in good shape and repair, with an eye on plumbing is the best thing you can do."

Tips on Mold

• Check your crawl space every six months to make sure pipes aren't leaking.

• Keep your roof, windows, gutters and siding in good repair to avoid leaks.

• If condensation shows up on windows, wipe it off, to keep the humidity down.

• Get a dehumidifier if you don't have central air conditioning.

• Don't assume opening the windows will dry out a humid house or room.

• If the humidity is higher than 60 percent outside, don't open the windows.

• Should mold occur on a nonporous surface such as plastic, glass or metal, it's growing on a organic matter such as a thin layer of soil. Clean it off with a mild detergent such as 2 caps of dishwashing soap in a gallon of water.

• On semiporous surfaces, such as hardwood floors, particle board or plywood, wiping isn't enough. Use a vacuum with a HEPA filter to get off as much of the mold as possible, then sand the wood cleanly.

• On porous surfaces, such as dry wall, wiping, vacuuming and wire brushing may not be sufficient. The portion of wall may require replacement.