How is impact-absorbing playground surfacing tested in the laboratory and on site?
BS EN 1177 sets out two test procedures for impact-absorbing playground surfacing, one conducted in the laboratory and one carried out on site. The laboratory procedure establishes the critical fall height of a surfacing system. The on-site procedure checks at selected locations whether an installed area covers the free fall height of the equipment present. Test specimens with a combined area of at least one square metre are placed on a level, rigid concrete base. Loose-fill surfacing, such as impact-absorbing sand, gravel and woodchips, is installed at its intended depth. Safety tiles are laid so that the joints between tiles are included in the test.
Laboratory impact testing uses a hemispherical 4.6 kg test head, approximately 16 cm in diameter, fitted with an accelerometer, dropped from different heights onto the surfacing. For safety tiles, at least nine drops from at least four heights are made at separate locations 25 cm apart. For loose-fill surfacing, three impacts at each height are made on the same location. Testing is performed at 23 degrees Celsius, with a permitted variation of up to five degrees.
Laboratory results are assessed against the HIC value, which is the head injury criterion, and peak acceleration gmax. The critical fall height is the height at which either HIC 1000 or gmax 200 g is reached, with the lower value governing. It is established by interpolation of the measurement series. The test report gives the critical fall height in metres to two decimal places and states the test laboratory's measurement uncertainty. The result applies only to the tested construction, including tile type, thickness and connection, or, for multilayer systems, the complete layer sequence. The test substrate is the rigid laboratory base, not the site-built construction.
On-site testing verifies whether an installed impact-absorbing playground surfacing covers the free fall height of the equipment present. The test fall height must be at least the free fall height specified for the item of playground equipment under BS EN 1176. Measurements are taken at the least favourable locations, such as areas where the surfacing is worn or where its depth is lowest, and at further representative locations. The number of test locations depends on the size of the impact area, for which the standard specifies a minimum number. This procedure applies only to the locations tested and does not establish a critical fall height.