Triggering a Trap
All traps have a defined trigger. If the characters fail to locate a trap while exploring an area, the trap might be triggered by a standard part of traveling, such as stepping on a floor plate or moving through a magical sensor. Some traps instead have touch triggers. These traps trigger only when a character deliberately takes an action that directly manipulates the environment—by opening a door or pulling a chain, for example.
Source
Core Rulebook pg. 410
