Zone of Sweet Air

Zone of sweet air creates an invisible barrier around the area of effect that repels all noxious elements from poisonous vapors, including those created magically (such as a Stinking Cloud). The spell offers no protection against poisonous vapors created by a dragon's breath weapon (such as the chlorine gas of a green dragon). Noxious gases already within the area of effect when the spell is cast are not affected. Fresh air passes into the area normally.
If a poisonous vapor is expelled within the area of effect (for example, a stinking cloud is cast), the spell takes effect normally but dissipates in half the time normally required.
The spell affects a cube whose sides equal the caster's level times 10 feet (for instance, a 10th-level caster could affect a cube whose sides are 100 feet long).

[Tome of Magic]

Sphere; Wards
(Abjuration)
Level: 3

Range: 10 yards/level
Components: V, S, M
Duration: 1 turn/level
Casting Time: 3
Area of Effect: 10-foot cube/level
Saving Throw: None

Material Components:
the priest's holy symbol, a silk handkerchief, and a strand of spider web