Fire trap creates a fiery explosion when an intruder opens the item that the trap protects. A fire trap spell can ward any object that can be opened and closed.
When casting fire trap, you select a point on the object as the spell's center. When someone other than you opens the object, a fiery explosion fills the area within a 5-foot radius around the spell's center. The flames deal 1d4 points of fire damage + 1 point per caster level (maximum +20). The item protected by the trap is not harmed by this explosion.
A fire-trapped item cannot have a second closure or warding spell placed on it. A knock spell does not bypass a fire trap. An unsuccessful dispel magic spell does not detonate the spell. Underwater, this ward deals half damage and creates a large cloud of steam.
You can use the fire-trapped object without discharging it, as can any individual to whom the object was specifically attuned when cast. Attuning a fire-trapped object to an individual usually involves setting a password that you can share with friends.