Zinsser Mold Killing Primer is a protective, water-based coating that can be applied directly over existing mold, mildew and odor-causing bacteria. Featuring a proven, registered and approved antimicrobial-fungicidal agent, it not only covers over associated stains but also kills all pre-existing fungal organisms. Use it directly on nearly any dry, debris-free, non-porous, interior or exterior surface with minimal pre-cleaning in just about any residential, commercial or industrial environment: homes, offices buildings, retail establishments, schools, hospitals, factories and more. And though this primer is compatible with any topcoat product, it pairs perfectly with Zinsser PERMA-WHITE Mold & Mildew-Proof paints. To fully cover over and obscure heavy stains, particularly those caused by water leaks, a second primer coat with a tailored, stain-blocking product may be required. In such scenarios, BIN and Cover Stain primers are highly recommended.