The fibers used for a carpet's face yarn dramatically affect its look and performance. Although some face yarns employ wool, approximately 97% of contemporary carpets utilize only synthetic fibers. Some yarns blend fibers; for example, acrylic may be blended with wool.

The list of synthetic fibers can be confusing because manufacturers often tag them with proprietary trade names such as Trevira or Anso. To simplify, just recognize that all synthetics fall into four generic categories: nylon, olefin, acrylic, and polyester. The fiber content is listed on a carpet's specification sheet.

Synthetic fibers used to look...well, synthetic. But these materials have improved by leaps and bounds since their advent more than 50 years ago. First, the shape of nylon fibers was altered to reduce unwanted sheen; then, anti-static fibers were added to cut down on the buildup of static electricity.

In recent years, chemicals such as Scotchgard Stain Release have been added to resist soil and stains, and some fibers have been given a built-in molecular barrier that resists stains and soil (DuPont's Stainmaster was the first of these processes). Such treatments allow spills to remain on the surface a little longer, minimizing the possibility of staining.