CSA Z614, 10.2 – critical height;

The surfacing material used within the protective surfacing zone of the piece of playground equipment shall have a critical height of at least the defined fall height.

In order for a protective surface to be compliant with our standard, it must have a critical height of at least the defined fall height of the equipment it serves. Therefore, the critical height of the surface must be known prior to first use of the playspace and when compliance is claimed.

So how can the critical height be known? The standard states that the test methods specified in ASTM F 1292 and CEN EN 1177 are the acceptable methods for testing protective surfacing. ASTM F 1292 specifies that critical height testing can only be done under laboratory conditions and at the specific ambient temperatures. The critical height test results can be supplied by the product manufacturer or testing can be commissioned by the owner/operator or their designate.

The study has relied on the information given on table 1 in the Z614-98 standard as the source of critical height data. While this source is not suitable for a claim of compliance, let’s take a closer look at this action by the study:

The study shows its defined fall height as a range of 2.13 meters to 2.18 meters and a compressed surface depth of 178mm (7 inches). The data also shows that 27.5% percent
of the surfaces did not even meet this 7 inch threshold. The author has advised that “the surfaces were constructed with an eight inch fill depth”.

Table 1 of Z614-98 shows that a 225 mm (9 inches) compressed depth of EWF produces a critical height of 1.8 meters. In other words, at surface thicknesses below 9 inches and at fall heights above 1.8 meters the surface will fail.

Using this table, the surfaces in the study are a FAIL. The manufacturer and the TDSB specifications require a compacted EWF depth of 300 mm. The Z614-07 version of the standard which was in effect at the time of the study specifically recommends a compacted depth of 300 mm (11.81 inches). There is no measure anywhere, in any of the
3 versions of CSA Z614 that suggests EWF at a compressed depth of 7 inches would have a compliant critical height.

It’s like taking a trampoline and cutting its legs down so that it is, say, 1 foot above the ground and then standing back to count the broken ankles. Then, in turn, saying ‘see’, this trampoline is not as good at reducing broken ankles as some other trampolines. It is elementary and straightforward that the trampoline was never designed to have its legs cut off. Reliable observations and conclusions about a product cannot be gleaned from its improper use. Unfortunately, this is what the study has done. Itis part of the reason why it is a failed document and why it should be removed from publication.