Airtight Architecture (3.5e Spell)

''Outside, the Plane of Fire roared and broiled violently. Thank god the trains in the City of Brass were protected from those flames.''

Believed to be based off the same magic which protects the City of Brass from the Plane of Fire, this spell renders a structure, building, or vehicle airtight even if it otherwise has small holes, cracks, or other paths of entry up to 1 inch diameter. The area inside the warded structure is set to the same temperature and conditions as when the spell was cast with oxygen being recycled and refreshed, unhampered by the ambient conditions outside.

If a door is opened or the insides are exposed, the insides are affected normally by external conditions until the door or entry is sealed again. Conditions return to normal within 1d4 rounds.

This spell protects those inside the structure but not the structure itself. The structure could still be damaged by external conditions, and subsequently create a breach from the damage.

If this spell is cast as a 5th level spell, the duration becomes 1 day/level. If cast as a 6th level spell it becomes Permanent. If cast as a 7th level spell, it becomes Instantaneous.