Poured Rubber and the Playground Fall Zone
June 30, 2020
The Playground Fall Zone-
Constructing almost any structure usually involves maintaining standards in order to curb the potential for disaster. In houses, there are numerous objects from walls, plumbing, electrical, etc which must all be subject to the same quality standard. The same thing happens in workplaces as well, where environments are reviewed in order to see if they pose a threat to the life of workers. The same applies to structures built for leisure, like swimming pools and playgrounds.
Yet playgrounds are a primal place. The structures built on them are often raised to a significant height from the ground; This is amplified through the physical limitations of a child.
Likewise, these high structures facilitate options that cause fast movement at a suspended height such as slides, monkey bars, rope ladders, ect. A fall is inevitable in such scenarios, and how high/ what material the child falls on can make a significant impact on their health. This is why the term ‘fall zone’ and ‘critical fall height’ have been created as a way of measuring a safety standard to minimize injury.
What is Required by Law:
In Ontario, playgrounds/ play structures are subject to following agreed-upon safety codes in regards to the ‘fall height’ of a play structure. This can vary depending on the size and intention of the play facility, however, some statistics and common sense offer the same wisdom.
Critical Fall Height-
The critical fall height is considered to be the max height/ fall from a play structure that is most likely to incur a serious injury. Typically, any structure exceeding the height of 1.5 meters almost doubles the amount and severity of injuries that children receive. Among those, head injuries are the most serious and are the reason fall height/ fall distance regulations are maintained.
There are two factors that affect Critical fall height; They are the height from the structure’s base up to the brink (the height jumped from), and the depth of the surface material (which directly interferes with shock absorption.
Shock-absorbing materials tend to be set into the ground deeper in relation to the increase of height. This is because there is a minimal level of depth needed to functionally absorb, and re-distribute the potential energy of a fall.
Common Dangers of the Playground:
-Coarse or non-shock absorbing materials which do not prevent scrapes, fractures, or bone breaks.
-Loose items, potholes, or roots which serve as tripping hazards
-Improper drainage, which can disrupt the shock absorption of certain surfaces, or negate it completely.
Fall Shock Absorption by Common Surface-
This is a general list of commonly used playground materials, however here is a more detailed article describing the materials.
Poured rubber is a common material seen in most playgrounds due to its great shock-absorbing properties. Poured rubber is often made out of shredded EPDM granules mixed with a bonding agent, which can then be stacked on top of other shock absorbers in order to provide the maximum fall-control.
Another bonus to this cake-layer structure of poured rubber is consistency. With other commonly used materials such a pea-gravel or wood chips, the shock-absorbing qualities can be altered by natural processes. As mentioned before, shock absorption is dependant on the layers (how deep) the surface material is to store potential energy. Pea gravel, wood chips, sand and other loose natural materials can shift depending on the elements, and thus provide uneven absorption.
Poured rubber solves this by being a singular, flat, bonded mass that cannot be altered. Once fitted, the rubber surface sticks to the shape it was molded into, as well as its depths. Some brands of poured rubber offer shock absorption for falls at 16 feet
Poured rubber surfaces are also slip-resistant, avoiding the common problem of playground floods which may further destabilize the materials
A Playground with Poured Rubber Foundation- Excellent Shock Absorption
Scattered substances like pea-gravel, sand, and dirt rely on their accumulation in order to distribute shock. For pea gravel the engineering relies on small, smooth stones to take on the impact, while also providing a non-abrasive surface to fall on. These tiny rocks can still embed themselves if contacted at high velocity, and can become flooded in the presence of rain.
Sand in particular is a popular choice for its softness, though this can easily change to a mud-like granular substance in the presence of rain. Regardless, the pillowy aspects of dry, warm sand are an easy and plentiful resource for playground safety.
Wood chips are an excellent natural material that can be heaped up in order to provide ample absorption, and insulation. Wood chips are used because they are a natural and affordable surface that spreads easily, and thus follows some of the same disadvantages as sand or pea gravel.
Surfaces to Never Use:
The pavement is high risk because of its density and coarseness, which offer little to no shock absorption, while also causing scrapes and cuts. Further damages that are commonly received are broken bones, fractures, and dislocations. While the material is consistent and relatively slip-proof, it is the least compatible substance to use when considering the potential for injury.
The Coarse Surface of Pavement Causes Additional Injury
These very natural substances are not an issue for normal sports such as running, soccer, ect. They even provide a natural amount of shock absorption, though it is negligible to other materials which are designed for safety. In terms of compacted dirt, due its density it is almost just as dangerous as falling on concrete.
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