(a) There must be loose-fill surfacing material or unitary surfacing material in the use zones for all climbing, rocking, rotating, bouncing, or moving equipment, slides, and swings. Loose-fill surfacing materials include loose particles such as sand, pea gravel, shredded wood products, and shredded rubber.(b) You must not install loose-fill surfacing materials over concrete or asphalt.(c) If you use loose-fill surfacing materials, you must install nine inches or more of uncompressed loose-fill material in the use zones.(d) You must ensure nine inches of the loose-fill materials are maintained at all times.(e) You must mark all equipment support posts to indicate the depth at which the loose-fill surfacing material must be maintained.(f) If you use unitary materials, they must be installed and maintained according to manufacturer's specifications. Unitary surfacing materials are manufactured materials including rubber tiles, mats, or poured-in-place materials cured to form a unitary shock-absorbing surface.(g) Unitary materials may be installed over concrete or asphalt only if recommended by the manufacturer.