how does this activate when colided with

float force_amount = 999999999999999999999999999999.0;

default
{
on_rez(integer start_param)
{
llPreloadSound("Explosion");
}
collision_start(integer total_number)
{
llSetDamage(5000);
if (llDetectedType(0) & AGENT)
llPushObject(llDetectedKey(0), force_amount*llRot2Up(llGetRot()), ZERO_VECTOR, FALSE);
llTriggerSound("Explosion", 10.0);
llMakeExplosion(20, 1.0, 5, 3.0, 1.0, "Smoke", ZERO_VECTOR);
llMakeExplosion(20, 1.0, 5, 3.0, 1.0, "fire", ZERO_VECTOR);
llDie();
}
}