That spell is trap worthy also. maby create a slightly more powerful version that causes the material to ignite at a later date.
just a quick "Delayed" Version of the spell
Delayed Carpet of Flame
Level: wiz/sorc 7
Casting Time: 1 hour (not intended for combat use)
Duration: 24 hours or when triggered, wichever occurs first (the ammount of delay it has)
This spell functions exactly like carpet of Flame except that it is more powerful and can be detonated at a certain time within the duration, during a certain event(defined by the caster at the time of casting the spell), wichever happens first, or both. The flames of this spell can reach 2 feet high and deal 1d6 points of damage per level with a maximum of 15d6. The caster can not move the spell out of it's designated area. it follows the same ulse as "Carpet of Flames" for determinint extra damage besed on catching fire. The flames remain for one round per caster level.
Trigering the spell: to trigger the spell, the caster mearly states how many hours the spell remains dormant untill it ignites or what sort of event must be done to activate the spell; such as: a command word, the passing of any or a specific creature, or the death of the caster. this is essentialy left up to the imagination of the caster and the Dm. prior to detonation, the area to be ignited looks perfectly normal, though detect magic spells reveile the presence of the spell.
Arcane components: one large ruby costing no less then 1,000 gold, crushed and sprinkled over the area to be covered (not nessisarily compleatly covered)
That was just quickly whiped up. more so a suppliment to the carpet of Flames spell then a redon version.