Yes, but when you're inside the gas cloud it specifically says on the pop up message that you're being poisoned.
Poison is versitile, in the effect that it can have two totally different meanings:
1.) Poison of the
blood; the poison courses through the blood stream, with the capability of effecting every major organ in it's path.
2.) Poison of the
flesh (for lack of better terms); the posion corrodes, or eats away, at whatever it touches, the most common form of this type of poison is an airborne solvent.
The perk only, or at least should only, effect Posion's of the blood, mainly because it's the heart, it moves the blood throughout your body, which makes sense for blood-rooted poisons to be filtered out. For something like the cloud to not effect you, you'd need some sort of filter for your epidermis and lungs, though, taking into account the nature of The Cloud, creating this would be virtually impossible.