A filter for filtering a fluid in a substrate processing apparatus comprises first and second stages that are connected to one another. A delivery system provides a vaporized liquid to the filter. The first stage of the filter comprises a basic compound, and the second stage of the filter comprises a desiccant. A second filter comprises a permeation filter with permeable membrane to filter the fluid. Methods of filtering the fluid to reduce formation of undesirable process residues using the filter(s) are also described.