You can set the system to always place a trap on a specific door or placeable by setting a local on the object "TRAP_ALWAYS = 1", most of the info for the system can be located in se_respawn_trap.nss. Alphamojo is also correct that setting "TRAP_NEVER = 1" will never alow the system to place a trap on the door or placeable. Additionally, an invis object with the tag INVIS_TRAP_SPAWNER_RANDOM must be placed in the area. Set a local variable int TRAP_PERCENTILE equal to the percent chance ou want traps to be set. A value of 25 = 25% chance of an object having a trap set upon it.