Potassium permanganate is an oxidizing substance that can remove odors and gases from the air. It is sometimes used as an additive to air purifier carbon filters, to increase the range of gases that can be removed.
Activated carbon is effective at removing benzene, formaldehyde and many other VOCs (volatile organic compounds), but is less efficient at removing gases that are made up of sulfur compounds such as hydrogen sulfide and sulfur dioxide. For situations where sulfur compounds or odors are an acute problem, potassium permanganate can be used in addition to activated carbon.
Potassium permanganate is generally not needed in most household or commercial environments. Specific situations where potassium permanganate filters may be useful include natural gas leaks and/or when very strong sulfurous odors are present.