Critical Height

Critical Height

Falls from playground equipment are the most frequent type of injury to children on playgrounds and head injuries are the most frequent cause of death in playground equipment-related falls. The ASTM International (ASTM) Standard F1292 is designed to provide a testing method for surfacing materials that will allow assessment of impact attenuation of playground surfacing and thus reduce the severity and frequency of fall-related head injuries.1 The term “Critical Height” is the key to understanding the purpose and method described in ASTM F1292.

Critical height is defined as “…the maximum fall height from which a life threatening head injury would not be expected to occur.” Fall height is “…the vertical distance between a designated play surface and the playground surface beneath it.”2

Fall heights of various kinds of play equipment are identified in the U.S. Consumer Product Safety Commission (CPSC) publication “Public Playground Safety Handbook” in Section 5 under each type of equipment.3

The purpose of critical height ratings is to approximate the maximum fall height that would not result in a life threatening head injury.4

Critical height is determined by a combined measurement of acceleration (shock) of an impact and the duration of the impact as it relates to head injury. The shock or force of the impact is measured in “g’s” which is the acceleration due to gravity. The maximum peak deceleration before a debilitating head injury might occur is 200 g’s. HIC, Head Injury Criteria, measures the time of deceleration. The value of the HIC must be less than 1000 to avoid a life threatening head injury.5

The testing for critical height is typically done in a laboratory, however, testing may also be done in the field using the F1292 testing methodology.6 Playground bid specifications are starting to require field testing prior to completion of installation. In addition, playground injury litigation sometimes requires surface field testing in cases of injury caused by falls to the surface from play equipment.

The responsibilities for conformance with critical height ratings are as follows:

  • Manufacturers and installers are responsible for providing critical height ratings for surface products.7
  • Owner/operators are responsible for having protective surfacing installed that meets the fall height requirements of the equipment.8

Having an adequate and appropriate playground surface and maintaining it properly are the most important things a playground owner/operator can do to minimize the severity of playground injuries.

  • 1. ASTM International (ASTM) Standard F1292-13. “Standard Specification for Impact Attenuation of Surfacing Materials Within the Use Zone of Playground Equipment,” Introduction, p. 1.
  • 2. Ibid. ASTM F1292-13, Section 3, p. 2.
  • 3. U.S. Consumer Product Safety Commission (CPSC) publication No. 325-10. “Public Playground Safety Handbook,” Section 5.3, pp. 24-41.
  • 4. Ibid. U.S. CPSC 325-10, Section 2.4, p. 8.
  • 5. Op. cit., ASTM F1292-13, Section 4, p. 4.
  • 6. Op. cit., ASTM F1292-13, Section 1, pp. 1-2.
  • 7. Op. cit., U.S. CPSC 325-10, Section 2.4, p. 8.
  • 8. ASTM International (ASTM) Standard F1487-11. “Standard Consumer Safety Performance Specification for Playground Equipment for Public Use,” Section 11.2.2, p. 17.