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Playground Surfacing Material

The surfacing under and around playground equipment can be a major factor in determining the injury-causing potential of a fall. Children's center of gravity is higher than adults, and as such, children fall head first. The more shock-absorbing a surface can be, the less likelihood of serious injury.

The most widely tested method for evaluating the shock absorbing qualities of playground surfacing material is to drop an instrumented headform onto a sample of the material and record the acceleration/time pulse during the impact. Such a method is described in ASTM Standard Specification for Impact Attenuation of Surface Systems Under and Around Playground Equipment, American Society for Testing and Materials ASTM F1292.

Critical height is a term originating from Europe and is used to describe the shock performance of a surfacing material. Critical height can be considered an approximation of the maximum fall height from which a life-threatening head injury would not be expected to occur. Surfacing materials around play equipment should have a critical height value of the highest accessible part of the equipment. For a swing, the highest accessible part of the swing structure is the height of the pivot point where the swing's suspending elements connect to the supporting structure. Since children are expected to climb guard rails on climbing structures, the highest accessible part of the platform surrounded by guard rails is the height above the playing surface of the top of the guardrail.

Acceptable surfacing materials that absorb impact and meet the American's with Disabilities requirements for accessible routing fall into two categories:

• Unitary Materials - generally stationary systems of rubber tiles or a poured in place rubber impact surface. These systems are very expensive, but require little maintenance. They can however be easily vandalized. The tiles sometimes can shift with the weather and cause tripping hazards. The height of the rubber will be determined by the critical fall height for example, 2 1/2 " of surfacing is necessary for a six-foot fall height.
• Loose-Fill Materials - also have acceptable shock absorbing properties when installed at the proper depth. Engineered wood fiber is finely shredded wood material that holds together when compressed and is the only loose fill material to meet the American's with Disabilities requirements for accessibility. It is safe to use it around plant materials as mulch. It is much less expensive than unitary materials, but since it is a natural material, it does decompose over time. A disadvantage is that engineered wood fiber requires the use of permanently affixed mats in high use areas. Engineered wood fiber goes by such trade names of Wood Carpet or Fibar. Generally speaking, for early childhood play yards, the depth of the material would be 12" uncompressed.

The proper use of impact absorbing materials whether unitary or loose-fill will greatly reduce the risk of children being seriously injured when falling from play yard equipment. Background information for this article was provided by the Consumer Product Safety Commission, which is charged with reducing unreasonable risks of injury associated with consumer products.

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