According to the U.S. Consumer Product Safety Commission, more than 156,000 children require emergency medical care each year because of playground injuries. One of the most important factors in preventing serious injury is the use of playground mulch. CPSC guidelines concerning playground materials include rules about critical height, toxicity, minimum fill depth, maintenance and playground preparation.
Critical Height Testing
The shock absorbency of playground materials is determined by the ASTM 1292 test, which measures the level of impact a metal headform receives when dropped onto a specific surface from a certain height. For example, 9 inches of sand only provides adequate shock absorbency at a fall height of 4 feet, while 9 inches of recycled rubber has a critical height absorbency rate of 10 feet. The recycled rubber provides more protection from falls, making it a better choice for larger playground structures.
Playground mulches are required to meet certain rules concerning toxicity. Specifically, wood mulch treated with chromated copper arsenate (CCA) is prohibited. Questionable mulch should not be used.
Concerns about the safety of recycled rubber mulch have prompted several studies. One recent limited-scale scoping study from the EPA shows no adverse reactions to humans when exposed to recycled rubber mulch. The Centers for Disease Control and Prevention, as well as the Consumer Product Safety Commission, recommend that young children wash their hands after playing on these surfaces, especially before eating.
Minimum Fill Depth
The minimum fill depth for all playground mulches is 9 inches. However, mulches compress and settle with time, so the recommended initial depth is 12 inches.
Maintenance of Mulch
Playground mulches require constant maintenance to ensure adequate shock absorbency. Areas under swings and slides become bare and must be refilled. Mulches can become compacted and unlevel and should be raked regularly. Cold, frozen ground underneath the mulch will reduce shock absorbency. In northern climates, consider adding more mulch. Also, mulch must be replaced when necessary to keep it at the minimum 9-inch level.
Choose a level site with good drainage for the playground. Avoid areas with heavy sun exposure. Do not lay mulch over asphalt or concrete. When laying mulch over compacted dirt, apply a layer of gravel, followed by geotextile fabric. Lay protective mats under swings and slides. Add mulch last.