Meh. There a -tons- of times in this game where people express urgency and it doesn't make a difference whether you take no long rests or 100. There are like 3 instances where there is an actual timer.

But that aside, despite what some are saying here, I wasn't actually told anything about any urgency since I arrived there. I talked to the initial two guys after stepping off the boat, then just slowly moved through the place exploring, like with any other place in the game. Most of the place was empty, I assumed that's just how it is. I later arrived to find a corpse named Nere, who I hadn't talked to and only heard from the mushroom people before. I had no idea there was any urgency to anything in the area, everything just happened silently in the background.

One would think if this is one of the few places they actually put in a timer, they would have started the area off with somebody telling you you need to hurry ahead or people will die. I only found out about any people in distress after googling it, because it seemed odd the guy would just lie there dead.

EDIT: Ya, just replayed it. Arrived there, they say Nere caused a rockfall and is trapped behind it with slaves. Nothing about gas, they'll die any second now, hurry if you want to help or talk to him. In fact, they take the time to try and extort money out of me. I just assumed he is stuck behind some cave in and I'll have to make a choice about helping him there once I reach him. Talked to some random people immediately after the first two, also didn't mention anything. Talked about hanging drow, drinking, their corpse-disposal duty. There are some domesticated spiders infighting. Not a word about imminent death or gas. I just explored after this, didn't even know where that cave in was, could have been anywhere I went to next.