Increased odor-fighting protection with the power of Febreze for multi-cat litter boxes. 10-day Odor Control GUARANTEED. Leaves behind a fresh clean scent. Now with Ammonia Block! Ammonia Block technology from Fresh Step stops odors from one of the primary odor offenders in your litter box: cat urine. Working in two ways, this technology controls bacterial growth, while also deactivating the enzyme that forms ammonia. What does it all mean for you? A litter that keeps ammonia odors away from your litter box and home.