Many PVC-free resilient flooring options have been introduced to the market, including those produced with different synthetic polymers. The specific polymer used can vary widely and may include polyethylene, polypropylene, ethylene vinyl acetate, acrylics, and polyurethane (see the All Contents tab for more information). Different polymers may pose different concerns in terms of residual catalysts or monomers in the finished product. PVC-free resilient flooring can be homogeneous (the same composition throughout) or heterogeneous (with layers of different composition within the flooring). This CP focuses on heterogeneous floors in either sheet or tile form. Heterogeneous floors typically have a wear layer that includes a UV-cured topcoat, a print layer with printed ink or other pigmentation on paper or polymer film, and a base layer or layers. They also commonly have fiberglass reinforcement and some may have an additional backing material. Many different pigments are used to achieve various color combinations and these pigments may bring with them additional hazards. These products are typically commercial-rated for use in commercial or residential applications such as healthcare, senior living, office, retail, hospitality, education, and housing. They are commonly certified to have low VOC emissions per the California Departement of Public Health (CDPH) standard through certifications like FloorScore and GreenGuard Gold. A few products contain some pre- or post-consumer recycled content or biobased content. Most products are installed with an adhesive, but some "click" installed tiles or floating floors are available. Heterogeneous PVC-free flooring typically does not require waxing or polishing.