A safe play environment is essential. To determine whether a surface offers sufficient impact attenuation, we refer to the European EN 1177 standard. This standard describes two specific test methods for performing HIC (Head Injury Criterion) measurements. In this article, we dive deeper into these methods and the role of the Gmax value.

Method 1: Calculating the Critical Fall Height of the Surface

The first method described in the EN 1177 standard is used to calculate the exact Critical Fall Height (CFH) of the surface. This is an accurate way to determine the maximum height from which the surface is considered safe.

How does this HIC test work?

To determine the critical fall height, you must perform at least 4 HIC drops in a single session. For a reliable result, ensure a sufficient spread in the drop heights. Ideally, two of these measurements should result in a HIC value above 1000.

Important: The fact that the HIC value exceeds 1000 during testing does not immediately mean the surface has failed. This data is actually necessary to calculate a curve (graph). From this curve, you can determine the actual critical fall height of the surface (the point where the line intersects with the 1000 HIC limit).

Comparison with the Playground Equipment

Once you have calculated the critical fall height of the surface, compare it with the certificate of the playground equipment:

• The certificate states the maximum free fall height of the equipment.

• Is the Critical Fall Height of the surface higher than the fall height of the equipment? Then the surface is safe and approved.

The Influence of Gmax Value (Since 2018)

Since the revision of the standard in 2018, the HIC value is not the only leading factor. The peak acceleration, expressed in Gmax, is also of great importance.

Using the same measurements, a fall height is also calculated based on a Gmax value of 200. The rule is simple: the lowest critical fall height is the determining factor.

• Usually, the limit is determined by the HIC value.

• However, with very hard or stiff surfaces, the Gmax limit (200) may be reached before the HIC limit (1000). In that case, the Gmax determines the maximum fall height.

(Insert the graph here for explanation and use the Alt-text: "Graph showing the relationship between HIC value, Gmax, and Critical Fall Height")

Method 2: Quick Check for Existing Playgrounds

Method 2 was developed to quickly and efficiently verify if an existing surface is still sufficiently safe. This method is often used during periodic inspections of playgrounds.

The 'Drop Test' Procedure

With this method, the reasoning is reversed. You already know which equipment is present and what its corresponding fall height is (found on the certificate or data plate).

1. Take the fall height of the equipment.

2. Add a 10% safety margin to this height.

3. Drop the HIC meter from this calculated height.

The Result: Does the HIC value remain below 1000 AND the Gmax value below 200? Then the surface meets the requirements, and the playground is safe for use.