Sense Magic

 
Prerequisite(s): Spellcraft 1+ ranks
 
Benefit: You can sense whether an object you are handling or a creature you are touching is magical or under the effects of a spell… the very air might be magical in some places. As a full-round action, you can tell whether if an item is magical with a Spellcraft check (DC 20). A success informs you if there is magic present; a failure indicates that it is not. You cannot retry, take 10, or take 20 when using this feat.
 
 
Source: Mongoose Ultimate Feats