I say it's not. Other guy says it is. Not exactly sure about ruling.

"…an ingenious atmospheric interchange system that allows small portions of the surrounding air to be drawn into the helmet without compromising its protective seal."

So, yes, RAW, the Fenris-pattern helm as presented in RoB is still fully environmentally sealed, and could be used in toxic/no atmosphere without issue, the wearer simply has the option to 'sample' the outside air. While this means they could gas themselves, it'd be by choice.

It is sealed unless the Wolf opts to unseal it to smell a sample taking in the sampling chamber. If he chooses not to do that, he's not exposed to the outside environment.

And even if so, Astartes are virtually immune to air-based toxins, what with the hefty bonuses to the Toughness tests from organs and Unnatural Toughness, the free reroll from the Oolitic Kidney, and the option to Fate it.

Plasmafest hit it on the muzzle.

Wolf helms sample the air then redirect it to the marine. We can assume any harmful materials brought in with the odors are filters enough to make them safe for the puppie's sensitive nose.

herichimo said:

Auto-senses people. You don't need your own ears, eyes or noses in Astartes power armour, the wolf helm just has a far more sensitive air sensors than standard armour.

Auto senses analize the air then shows the user the analysis. Wolf helms lets some air in so the puppies can smell it for themselves. Its the difference between, "this air is 18% Oxygen 68% nitrogen, there is 200 parts per million of sulfer. Brothers, keep your helmets on, it must stink out there," and, "sniff sniff, Rwargh!! thats some foul smelling air, but I still caught the trail of our quarry, follow me!"

Both the Wolf Helm and the Wolf Sckull Helm are peices of gear you have to spend xp to get. (Either in the form of Sig Wargear for Wolf Helm or taking Wolf Priest for Wolf Skull Helm) So generally speaking if someone has to spend xp on it I tend to error on the side of cooler effect rather than not. Plus the rule for wolf helm specifically state it counts as sealed.

I don't recall a rule requiring signature wargear for the wolf pattern helm.

I consider it a hot fix used to remedy the problem of most circumstances denying the use of a basic solo mode, which was a really stupid problem to write into the game in the first place.

But it is consistent with the fluff, most Wolves won't wear their normal helmet because it dulls their senses.

As for acquisition, the helm isn't super powerful, so giving it out as a reward shouldn't be too big of a deal.

Kshatriya said:

This was my reading too. In the campaign I'm GM'ing, I gave it to the Space Wolf after his kill-team took down a Hive Tyrant, as a reward for going beyond duty.

DJSunhammer said:

Really? Most pics and minis I see of Space Wolves usually have 2/3 or more wearing normal helmets.

As all supra technology wolf helm aren't common gear.

Yes Space Wolf will get them as reward for their service but no red claw will have them.

Grey hunters and long fangs would get it. Because they are veteran warrior who know how to get the most of it.

Like all SM helm the Wolf helm is sealed, where is the need in a sealed armor to get a gaz leack just for your head…

But it can take sample of the air outside witout opening. So even when "open" it is still sealed. The fact being that if any toxin is in the air the wolf would suffer from them, but most of the time astartes physiology will prevail against the poison/toxin,…

I believe for all rule purposes the Wolf skull helm is considered sealed with the exception of allowing a space wolf your use his solo mode.