Have you ever stepped on board your RV or boat and noticed a smell from your black or gray holding tank? Have you used odor control products that do not work? With ODOR-SHOCK you can eliminate those smells like no other product. ODOR-SHOCK is environmentally safe and does not mask odors as it contains no fragrances or formaldehyde. ODOR-SHOCK eliminates odors by oxidation that neutralizes odors.