Helmet standards can be somewhat confusing.
National regulations for tree work may define a standard for helmets and can vary from country to country, some requiring helmets complying with the industrial standard (EN 397), others with the mountaineering standard (EN12492) – and some being non-specific.
Here is a helpful summary of the different helmet standards and examples for applications by Lyon Equipment:
Which standard is applicable for tree work is debatable.
There are a number of differences between the standards. The obvious ones being electrical insulation or molten metal splash conformance, but an interesting one is the way in which the chin strap and buckle release.
EN 397 (Industrial safety helmets) makes the following requirements of the buckle:
When tested in accordance with 6.9, the artificial jaw shall be released at a force of no less than 150 N and no more than 250 N, due to failure only of the anchorage(s).
So this means that the buckle shall retain the helmet on the head when a force of no less than 15 and no more than 25kg is applied.
As opposed to this, EN 12492 (Helmets for mountaineers) makes a different requirement of the buckle. In the testing procedure described under 5.7.3 of this standard the strap and buckle shall retain the helmet when a force of 50kg is applied for two minutes.
The idea behind this high-strength buckle is that it retains the helmet on the head of a climber in the eventuality of multiple impacts during a fall, rather than protecting from one hit, as with EN 397.
There are arguments for both… obviously a force applied to the head exceeding 50kg is likely to do substantial damage to the neck – that, and the helmet being ripped off the head by the initial impact is also reducing the peak force. This could be an argument for helmets conforming to EN 397 with its lower retention requirements, as mentioned above, between 15 and 25kg.
On the other hand, considering a fall or an uncontrolled pendular swing through the busy, cluttered structure of a tree canopy does raise the question whether there is an argument for a higher strength buckle in view of the risk of multiple impacts this type of scenario could entail.
Once again, this all just goes to show how, as soon as you start digging a bit deeper into standards, things get a bit more complicated than merely choosing between industrial vs. sport. Rather it is getting to grips with and gaining an understanding of the parameters described in the testing procedures and then, based upon that, deciding which standard best describes the intended use and therefore ticks the Fit for Purpose box.