How harmful is an insidious atmosphere?

An insidious atmosphere “requires the use of protective suits or vacc suits” (inherited from corrosive atmospheres) and “will defeat any personal protective measures in 2 to 12 hours.” (CT-TTB p.83, “Atmosphere”)

How harmful to a human is time spent in a corrosive or insidious atmosphere? Is it insta-death once the protective measures fail? Ongoing damage, which would quickly lead to unconsciousness, but perhaps your party can get you back to a safe environment?

Absent any rules-guidance on the matter, what sort of gaseous mixtures would be an “insidious” atmosphere, such that I can do my own RL research?

How does the Insidious Extra interact with the Weaken Power?

I’ve been playing around with the Weaken Power and trying to find its best application. As of right now, I think it’s in Weaken Senses. Almost every enhancement in Senses requires 1 rank at 1 point per rank and an unaugmented human has 11 or 12 ranks in senses (Acute, Accurate, Ranged vision/Acute, Radius, Ranged auditory/Radius olfactory/Accurate, Radius tactile/Close mental); with all this in mind, there would be virtually no situation where this wouldn’t be useful. However, I’ve also been experimenting with placing extras on Weaken; the one that caught my attention was Insidious, which prevents targets from understanding what exactly happened to them. My concern with this is whether or not this application of Weaken automatically violates Insidious‘s “feels fine until some deficiency makes it apparent that they are weaker” condition.

As such, Can Weaken Senses benefit from the Insidious Extra? If not, what do I need to do to have it benefit from Insidious?