Filter
(Abjuration)

Range: Touch
Components : V, M
Duration: 1 turn/level
Casting Time: 2
Area of Effect: 10-foot radius sphere
around creature touched
Saving throw: None

 This spell creates an invisible globe of protection that filters out all noxious elements from poisonous vapors; therefore, a creature protected by filter takes no damage and suffers no penalties from poison gas of any kind, including those created magically (such as stinking cloud). The exceptions are poisonous vapors created by a dragon's breath weapon (such as the chlorine gas of a green dragon); in these cases, the creature protected by filter suffers half-damage.
 The material components for this spell are a strand of spider web and a scrap of cotton cloth approximately one inch square.