Speaking of which:
Palladinium (obvious for whomever)
This is a silvery metal that can be molten quite easily to pour into the form of a sieve, or ground into a fine powder. In both cases the metal allows for a quick and efficient filtering of harmful substances into clean ones. If used as a sieve or fashioned in a mask you can use it to negate the effects of an aerosol attack like stinking cloud, cloudkill, fog cloud, et.al. Seeing how the metal is used as a catalyst to break the effects down it can be used indefinitely.
If ground into a fine powder and administrered to someone under effects of a disease, poison, ravage or affliction the effects can be negated. A dose of 1 teaspoon negates the effect of one disease (et. al).
A dose of Palladinium can be bought for 100 gp, the amount needed for a mask for a medium creature can be fashioned from 20 doses and requires a craft wondrous item crafting check of DC 28 and the maker must be in possession of the tools necessary costing 1000 gp.