Passive Notice
Passive Notice is a Non-Combat Activity using a type of Surveillance Actions that employs a character’s Perception to passively notice an object, area, or scene/interaction in order to discover something about it. It is done WITHOUT Concentration for a single round of Time. Characters can develop this types of action as Accomplished Activity.
Though most commonly it is a sight based check, it can be using any of the Senses, with their acuity (positive or negative) factored in as well.
iCore™i20™ Surveillance Details
Assuming the character is not totally distracted, their base chance to notice something important passively is 5 + bonuses.