What Houzz contributors are saying:
In some cases, cassette filters need to be cleaned with aggressive chemicals, such as sodium hydroxide (caustic soda). That is because these filters are made up of a mesh with small pores, which makes it difficult to remove the grime. One can clean a cassette filter by placing it in a deep tray and sprinkling some caustic soda on it. Now pour some boiling water in the tray and let it rest for two hours. After this, wash the filter with clean water, let it dry and put it back in the chimney hood.Caution: This method of cleaning should be professionally done, using rubber gloves and protective clothing. It is essential to keep some distance from the filters during the process of cleaning because caustic soda is highly corrosive and produces dangerous fumes which should not be inhaled.