Abstract: The present invention relates to an anti-bacterial and anti-dust coating for air ducting. In one embodiment, the anti-bacterial and anti-dust coating comprises: a polymer emulsion; a cross linking agent; a film forming agent; a filler and anti-dust agent; an anti-bacterial agent; hardener nanoparticles; a defoamer; and water. The anti-bacterial agent can be in powder or in liquid form. The coating can be applied on the inner surface of metal air ducting to reduce dust aggregation and prevent growth of bacteria, mold and mildew that causes stains and odors inside air ducting. With the aids of nanotechnology, various specific nanoparticles are added in the waterborne polymer emulsion to provide the anti-bacterial, anti-dust, anti-acid, anti-alkali, good flexibility and hardness for the coating. The product is also tested to be flame retardant and water resistance for increased safety in air ducts.