Hi,
The Vertex Vent and Vertex Best are the only two of Petzl's range that are rated for commercial use. The rest are sport models..
The link here is for their site..
http://www.petzl.com/en/pro/helmetsAny half decent outdoor/climbing shop will be able to sort you out. Don't be surprised though if shops don't stock the commercial range as therer's not a lot of turnover on it. A good store will be able to get in gear for you to try..
Personally, I have come across a few people (tree surgeons and mountain rescue mostly) who will still choose the sport models for the lightness and less bulk but we always advise them not to.
If you are in the EU then the ratings on Petzl's site will be correct but if you are in the US or AU then it would be worth checking the local regulations before purchase. I don't see it being a problem though, Petzl are globally accepted.
Either way, it could be an insurance nightmare if there is an accident involving someone wearing gear that's not covered..
Hope this helps..