Nemesis: Retaliation · Board game rules
How do Quoridors outside the map affect gameplay?
Quick answer
Corridors cannot exist outside the Facility's borders — they are simply never placed there, and any effect that would push an Intruder "outside the map" instead leaves it in place.
Details
The Facility is bounded by the Section and Round track border pieces, and no Room or Corridor can ever be placed on those pieces or beyond them [p.19 — Map]. This applies to all sides of the Facility, including the right and bottom edges [p.19 — Map].
Because of this, during the Exploration Sequence, if a card indicates a Corridor should be placed in a spot that lies outside the Facility's border, that Corridor is simply not set up — you skip it entirely [p.24 — Character Movement].
The only other place "outside the map" is referenced is with Repelling effects. If an Intruder would be Repelled out of an Unexplored Corridor and beyond the visible map, it instead just stays where it is — it's impossible to push it any farther [p.31 — Intruders].
Watch out: Since no Corridor tile ever actually exists outside the Facility, there's no gameplay space "outside the map" to move into, place Noise, or explore — any effect referencing such a space simply fails to apply or the Intruder stays put.