The FAQ says that a corrupted space becomes normal once a trap has been played on it .

Is the space still corrupted with respect to the trap damage?

The usual steps are (as I see it):

1 - Play card, pay threat, place trap prop under the hero ( = space no longer corrupted?).

2 - Hero gets to roll some dice, may receive damage and lose wounds (= threat for the OL or not?), may be displaced due to rubble token.

Parathion said:

I believe the trap should be resolved before any 'changes' are made, therefore the space counts as corrupted for the resolution of the trap card.

Not 100% certain though...

Corbon said:

From the faq:

Q: Is corrupted terrain an obstacle? Can the overlord play trap cards on it?
A: Corrupted terrain is treated as an empty space. Once a trap has been played on it, it no longer counts as corrupted.

I understand this to mean that at the moment the trap is played it ceases to be corrupted, and therefore no threat is generated for the damage caused by the trap. In order for a hero to fall into a pit, there has to first be a pit there, and hence it's no longer corrupted. I guess you could make a case that the rubble isn't there until AFTER it falls on the hero, but I still think this reads that when the trap is played (not resolved--which is when wounds occur) that it ceases to be corrupted.