Treetools sell Petzl Vent and Best helmets to arborists. Both helmets meet the ANSI Z89.1 2003 Type 1 (crown impact only) standard: Petzl Vent Class C - no protection against electrical current, and Petzl Best Class E - reduced danger from higher voltages and proof tested to 20,000 V.
Both helmets also reach the European Standard EN397 for for lateral deformation and -30° test with the Best also certified for electrical insulation and molten metal splash. Both are UIAA certified. The question is do they meet the AS/NZ 1801.1 standard used by most New Zealand companies as a "best practice' standard.
Answer: don't know!
It appears there are very few places where regulations or legislation require a product to carry the Standards Australia/New Zealand mark. In general the requirement is that the product 'conforms to the requirements of' a given standard 'or comply with' a given standard.
The Petzl helmets certainly reach this criteria as noted above. Treetools are unable to verify with Standards New Zealand or OSH that the EN397 standard is equal to or better than AS/NZ 1801.1. The preface of the AS/NZ 1801.1 states EN397 was referred to when the certification was drafted but that's about it.
Most arb companies accept the European standard. Anyway, the real redeeming feature of the Petzl helmets, from an arb perspective, is the superior chin strap system for securing the helmet to your head! Many similar 'certified' helmets are not suitable for arb work due to sub-standard chin straps. If anyone can help us verify the Standards situation further please advise.