Impact Attenuation

Impact attenuation of playground surfacing material is the measure of its shock absorbing properties. The shock absorbing properties are measured by dropping an instrumented metal headform onto the surface and recording the force of impact and the time of deceleration. The specifications for impact attenuation are found in ASTM International Standard F1292, “Standard Specification for Impact Attenuation of Surface Systems Under and Around Playground Equipment.”1

The purpose of the specification is to reduce the likelihood of life threatening head injuries. Head injuries are the most serious type of playground injuries. They are the most frequent cause of death from playground fall-related injuries.2 The instrument used to measure impact attenuation is called a Triax 2000. An instrumented headform, simulating a child’s head, is dropped from various heights. The readings from the instrument allow the person conducting the test to determine the critical height of the surface material. Critical height is defined as “…the fall height below which a life threatening head injury would not be expected to occur.”3

The testing for impact attenuation is usually done in a laboratory situation. Manufacturers submit samples of surfacing materials in various depths for testing. The test results are provided to surfacing customers who can then make an informed decision about the depth needed of their selected surfacing material, compared to the fall height of their play equipment, to be sure the surface has an appropriate critical height rating for the specific situation. Fall height is defined as “…the vertical distance between a designated play surface and the playground surface beneath it.”4

In some cases, impact attenuation testing can be done in the field. The Triax 2000 instrument is available for purchase so individuals or businesses can do field testing. Owners of older playgrounds who want to know whether the surface still maintains its necessary critical height rating have had field testing done. Playground bids often require field testing before first use.

  • 1. U.S. Consumer Product Safety Commission (CPSC) publication #325-10, “Public Playground Safety Handbook, Section 2.4, p. 8.
  • 2. ASTM International (ASTM), “Standard F 1292-13, “Standard Specification for Impact Attenuation of Surfacing Materials Within the Use Zone of Playground Equipment, Introduction, p. 1.
  • 3. Op. cit., CPSC, Section 2.4, p. 8.
  • 4. Op. cit., ASTM F1292-13, Terminology, 3.1.3, p. 2.