An unusual fog that is denser than air begins to fill a room should the people in the room walk out or crawl out

Walk out of the room because the fog will sink to the floor of the room

Walk out, because dense air sinks, cool air rises, so you should have enough air to breathe while walking out, better off, is to hold onto your breath and run out, or put something over your nose and mouth, whichever you use to breathe with, like a mask of some type of cloth. don't forget to stop, duck, and roll if the fires on you.