Just to give y'all and idea of how dangerous it is in there, twenty-three seconds is enough to hit the LD50/60. That's half of those exposed dead within sixty days. You'll feel queasy pretty quickly and will vomit and have uncontrollable diarrhea assuming you get out at that time. Even if you make it to those 60 days, you're still very likely to die within half a year.
You'll vomit uncontrollably within about thirty seconds. You may survive a week or two after that, assuming you get out immediately, and may even feel OK for a few days, but you will die a very painful death somewhere in that span.
One minute of exposure amounts to about nine-hundred Rems. That would kill you within the hour. You'll be unconscious in about that span. Left there a few minutes, you will die (mercifully) quickly.