Abstract: There is provided a formulation for sanitizing air and reducing malodour in the air. The formulation comprises a malodour absorbing compound, an antimicrobial compound, wherein the antimicrobial compound is chemically incompatible with the malodour absorbing compound when mixed alone together, a solubiliser, and a chelating agent for the malodour absorbing compound, wherein the chelating agent prevents the formation of precipitate or a cloudy solution when the malodour absorbing compound is mixed with the antimicrobial compound in the presence of the solubiliser.

Abstract: A method of preparing an antimicrobial air filter comprising the steps of: soaking a porous material in a silver nanoparticle colloid; and coating the porous material embedded with silver nanoparticles with a silane quaternary ammonium polymer such that the loss of silver nanoparticles is reduced. The resultant filter may be used in an air treatment device.