Carpet fibers can be either natural (wool) or synthetic (nylon, or even polyester made from recycled soda bottles). Matt Freeman-Gleason, founder of the Environmental Home Center in Seattle, says the best way to determine whether you'll be able to coexist with your carpet, especially if you're chemically sensitive, is to "use your nose. Take a sample home and live with it." Because chemical content can vary, ask for a sample from the production run of the carpet that you want to buy.

Carpet fibers are stitched into a primary backing, typically made from polypropylene. It's just one of the many synthetics used to make most carpeting, and the waste can be staggering: millions of gallons of water, tons of nonrecyclable scraps, vats full of dye dumped into the environment.

The synthetic latex used to hold the carpet together is what's most responsible for that "new carpet smell." It contains styrene, a known toxin, and other chemical compounds whose health effects (if any) have yet to be determined. Tests have been inconclusive at best, and none have really examined the effects of long-term exposure.

Properly selected padding muffles sound, adds softness, and actually extends the life of your carpet. Alex Wilson, executive editor at Environmental Building News, likes padding made from recycled polyurethane foam or natural jute. He says recycled rubber padding just plain stinks -- no really, it smells bad.

Something's got to keep your carpet down. That can be either an adhesive made from the same synthetic latex as above, or tack strips laid down at the edges of the room, onto which the carpet is stretched. You want the latter, which require professional installation but are ultimately better for you -- and for the planet.