Areas of the event site that players are prohibited from entering during gameplay. From the Accelerant core rules:
"Areas that are out of game are marked by the yellow or hazard orange signs with text marking it Out of Game. You may not enter these areas. The text of the sign indicates why, in game, this area cannot be entered. Some areas might be described as collapsed and ruined piles of rubble that have no real interior. Other areas might be marked as impassable swamp."
This allows staff to mark off restricted parts of an event site, while still allowing players to explain in character why they couldn't go in a particular area, rather than breaking character to say "we're not allowed over here".