Mold-resistant carpeting often is used in basements and areas of a home that tend to get wet. The concrete flooring in a basement draws in moisture and retains it in the carpeting, which provides a environment suitable for mold growth. Some molds such as black mold are a health concern for people with allergies and weakened immune systems. Good mildew- and mold-resistant carpets keep these molds from getting started.
A plastic fiber, acrylic feels like wool or cotton to the touch. It is naturally resistant to chemicals, soil stains and mold growth. It also resists fading in the sun and dries quickly. It's offered as an alternative to wool at a lower price point and is easier to clean and preserve than the natural fiber. Acrylic wears down and the pile flattens quickly, so it's not commonly used in carpeting since newer stronger fibers developed.
Over half the carpet sold in the United States is made of nylon. This fiber is made of a polyamide polymer and is resilient in high-traffic areas of the home. It naturally resists mildew growth and soil stains. Most nylon also is treated with a stain-resistant chemical to help prevent stains from household spills. Nylon costs more than other types of carpeting, but its longer wear and resiliency help it last longer than other carpeting.
This carpet is made from polypropylene, a product of gasoline refining. It's chemically inert and resistant to a wide range of chemicals and stains, including mold. It does tend to attract oil and quickly dirties in areas with oily soil or gasoline usage. It also tends to flatten easily and has a low melting point. This product should not be used in garages or near fireplaces, and avoid placing high temperature items on it. Olefin is used for outdoor carpeting.
Another plastic fiber, many polyester carpets are made from recycled plastic bottles. It's billed as an environmentally friendly carpet. Polyester tends to hold its color and is stain resistant. It's mold growth and chemical resistant. It's also strong, but the fibers aren't resilient to tread and have a tendency to flatten out. Polyester also attracts oily soils. New polyester has a plush, soft feel. It's cheaper than olefin and nylon, but offers some of the same stain resistant qualities.