Pure silica sand is one of the original infilling materials utilized in synthetic turf. Silica sand can either be coated with different materials as a standalone product or can be used to firm up in combination with traditional crumb rubber infill systems. It is most often used in arenas for sports that were originally or are normally played on grass. However, it is now being used on residential lawns and commercial applications as well. The main reason is maintenance—artificial turf stands up to heavy use, such as in sports, and requires no irrigation or trimming. Domed, covered, and partially covered stadiums may require artificial turf because of the difficulty of getting grass enough sunlight to stay healthy. Artificial turf does have its downside, however: limited life, periodic cleaning requirements, petroleum use, toxic chemicals from infill, and heightened health and safety concerns.