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Consider having any upholstered furniture, carpeting, or rugs that have a slightly musty smell (but no visible mold growth) treated with steam vapor (SV). A steam vapor cleaner looks like a vacuum cleaner, with canister, hose, wand, and head, but that's where the resemblance stops, because an SV machine does not vacuum up anything. The canister is really a kettle in which water is boiled and turned into vapor under pressure. Some vapor may condense in the hose, wand, and head, but what exits the cleaning head is very hot water vapor (hotter than 212°F, or 100°C), not liquid.
A traditional so-called steam carpet cleaner (the type that most professionals use and homeowners rent) is quite different. What comes out of the head is mostly hot water rather than steam. The water is squirted into the carpet and simultaneously extracted by a vacuum-cleaning suction device that is part of the cleaning head. If a carpet is "steam-cleaned" improperly by this method, the carpet and possibly the pad below become soaked with water. After a carpet has been properly treated with SV, however, it is barely damp, so there is less chance for fungal growth.
Because of the heat energy stored in pure hot vapor, a carpet properly treated with SV reaches a much higher temperature than one treated with hot water. Steam vapor treatment can kill up to 100 percent of insects [or arachnids] (mites, fleas, silverfish, booklice, and spiders) living in the carpet. If done slowly enough, SV can also kill some of the mold spores and bacteria, and it can denature (destroy) many of the allergenic enzymes in spores, as well as protein allergens in mite body parts and cat and dog dander. From a health perspective (though not necessarily from the carpet's perspective), I think SV is one of the safer carpet treatments available, because there are no chemicals (pesticides, fungicides, or antimicrobials) involved.
A few extra cautions are worth noting. Rugs on hardwood floors should not be treated in place with SV, because the high temperature and moisture may damage the wood finish. Hang a rug to treat it, or support it off the floor. In the winter you may have to ventilate the space while using steam vapor, to avoid condensation problems; in the summer you should ventilate the space well, or use air conditioning or a dehumidifier to lower relative humidity levels. Remember that the temperature of the vapor is at least 212°F, so be sure to check with the rug or carpet manufacturer before using SV (the high temperature of the steam can affect fibers and dyes, particularly in some synthetic carpets and rugs). If you can't obtain information about the carpet itself, you should test a small area that is not normally visible, where any damage caused by the steam will not be that noticeable. Finally, follow the SV equipment manufacturer's directions carefully for safe use.
Jeffrey C. May and Connie L. May; with a contribution by John J. Ouellette, M.D., and Charles E. Reed, M.D. - The Mold Survival Guide, pp. 184-186. © 2004 The Johns Hopkins University Press. Reproduced with permission of The Johns Hopkins University Press. (http://www.press.jhu.edu/books/title_pages/3335.html.)
