That was the one I was referring to, and it seems to me that it indicates a gas mask provides immunity to inhalation-vector toxins (even if they have another vector). Leaving something to the GM is a rather common aspect even when the general intention is relatively clear.
The mask wouldn't be quite worth its price if it only provided protection to inhalation-only toxins, though I understand some of the arguments behind it reducing the power of multi-vector toxins. Like I said, that's a house rule and my best understanding of 4E (and 5E treats things the same way) is that the gas mask provides immunity instead of partial protection. My meatspace group tends to rely on respirators (they ran out of gas masks twice and started to like using CS or Breathtaker gas after I used it against them a couple times) and they preferred the interpretation that gas masks only give full immunity to exclusively inhalation-vector and a reduction in multi-vector, likely because they've started stocking CS and know they'll have to take it again in the future as well. It's all "good enough" to me, I spend more of my time designing the spirits or drones that they'll be fighting against next week.
