Playground & Residential
Swing Sets Fall Protection Surfacing Materials Guide
The surface under and around playground
equipment can be a major factor in determining the injury-causing potential of a
fall. It is self evident that a fall onto a shock absorbing surface is less
likely to cause a serious injury than a fall onto a hard surface. Because head
impact injuries from a fall have the potential for being life threatening, the
more shock absorbing a surface can be made, the more is the likelihood that the
severity of the injury will be reduced. However, it should be recognized that all
injuries due to falls cannot be prevented no matter what playground surfacing
material is used.
The most important thing to determine when
trying to decide on a fall protection barrier is the Critical Height of the
different pieces of playground equipment. Critical Height is an approximation of
the maximum fall height from which a life-threatening head injury would not be
expected to occur.
The surfacing material used under and
around a particular piece of playground equipment should have a Critical Height
value of at least the height of the highest accessible part of the equipment.
Acceptability of Various Surfacing
Materials
Hard surfacing materials, such as asphalt
or concrete, are unsuitable for use under and around playground equipment of any
height unless they are required as a base for a shock absorbing unitary material
such as a rubber mat. Earth surfaces such as soils and hard packed dirt are also
not recommended because their shock absorbing properties can vary considerably
depending on climatic conditions such as moisture and temperature. Similarly,
grass and turf are not recommended because their effectiveness in absorbing shock
during a fall can be reduced considerably due to wear and environmental
conditions.
Acceptable playground surfacing materials
are available in two basic types, unitary or loose-fill.
Unitary Materials - are
generally rubber mats or a combination of rubber like materials held in place by
a binder that may be poured in place at the playground site and cures to form a
unitary shock absorbing surface. Unitary materials are available from a number of
different manufacturers many of whom have a range of materials with differing
shock absorbing properties. Persons wishing to install a unitary material as a
playground surface should request test data from the manufacturer that should
identify the Critical Height of the desired material. In addition, site
requirements should be obtained from the manufacturer because, as stated above,
some unitary materials require installation over a hard surface while for others
this is not required. Most are usually
too expensive for residential use.
Loose-Fill Materials - can
also have acceptable shock a, absorbing properties when installed at a sufficient
depth. These materials include, but are not confined to, screened sand, pea size
gravel, shredded rubber and shredded wood products. Loose-fill materials should not be installed over hard surfaces such as asphalt or
concrete.
Critical Heights of Tested Materials
The table below, lists the critical height
(expressed in feet) for each of seven materials when tested in an uncompressed
state at depths of 6, 9, and 12 inches. The table also reports the critical
height when a 9 inch depth of each material was tested in a compressed state.
The table should be read as follows: If,
for example, uncompressed wood mulch is used at a minimum depth of 6 inches, the
Critical Height is 7 feet. If 9 inches of uncompressed wood mulch is used, the
Critical height is 10 feet. It should be noted that, for some materials, the
Critical Height decreases when the material is compressed.
Table of Critical Heights (in feet) of
Tested Materials
|
Material
|
Uncompressed Depth |
Compressed Depth |
| 6 Inch |
9 Inch |
12 Inch |
9 Inch |
| Wood
Chips* |
7 |
10 |
11 |
10 |
| Shredded Bark Mulch |
6 |
10 |
11 |
7 |
| Engineered
Wood Fibers** |
6 |
7 |
>12 |
6 |
| Fine
Sand |
5 |
5 |
9 |
5 |
| Course
Sand |
5 |
5 |
6 |
4 |
| Fine
Gravel |
6 |
7 |
10 |
6 |
| Medium
Gravel |
5 |
5 |
6 |
5 |
| Shredded
Tires*** |
10-12 |
N/A |
N/A |
N/A |
| * |
This product was referred to
as Wood Mulch in previous versions of the handbook. The term
Wood Chips more accurately describes the product. |
| ** |
This product was referred to
as Uniform Wood Chips in previous versions of the
handbook. In the playground industry, the product is more
commonly known as Engineered Wood Fibers. |
| ***
|
This data is from tests
conducted by independent testing laboratories on a 6 inch depth of
uncompressed shredded tire samples produced by four
manufacturers. The test results reported critical heights which
varied from 10 feet to greater than 12 feet. It is recommended
that persons seeking to install shredded tires as a protective
surface request test data from the supplier showing the critical
heights of the material when it was tested in accordance with ASTM
F1292. |
The Critical Heights shown in the above
table may be used as a guide in selecting the type and depth of loose-fill
materials that will provide the necessary safety for equipment of various
heights. The depth of any loose fill material could be reduced during use
resulting in different shock-absorbing properties. For this reason, a margin of
safety should be considered in selecting a type and depth of material for a
specific use. By looking at the chart above it is easy to determine that a
shredded wood mulch product is the only product that will work under most swings,
slides and climbing equipment that will provide an adequate margin of safety.
Information Source: This article is an excerpt from the "Handbook for
Public Playground Safety", Pub. No. 325 U.S. Consumer Product Safety
Commission, Washington, DC 20207.
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