Comparison Lab: structured evidence audits for recurring odor-control decisions

Baking soda neutralizes whatever odor lands directly on the surface, then it is done. In a normally-stinky single-cat box that gets you about 12-24 hours before the smell is back.

Activated carbon does not neutralize anything. It traps odor molecules in a micropore network the size of a football field per teaspoon. Same teaspoon catches 92% of ammonia in controlled testing versus 15-20% for baking soda. Same teaspoon keeps working for 7-14 days because the network has not run out of trapping sites yet.

If the goal is one product per litter box, carbon does what baking soda is trying to do, only further and longer.

Zeolite is a real material with real ion-exchange chemistry. It does hold ammonia for a window. The window is just narrow: 38% capture in our testing, and the effect fades in 2-3 days as the exchange sites fill.

Activated carbon does not care whether a molecule is ammonia, mercaptan, or one of the other sulfur compounds in cat urine and feces. They all bond to the carbon surface. That is why the 92% number holds across the full odor mix, not just one molecule. Two to three times longer between refreshes is the second half of the story.

Zeolite is a fine moisture helper. As the full odor-control answer, it taps out fast.

Fresh Step leans on perfume plus a carbon claim. Arm and Hammer leans on baking soda. Both ask you to swap your entire 25 lb bag of litter ($12-25 a box) every month or so to get the odor benefit.

Purrify is an additive, not a litter. Sprinkle 2-3 tablespoons of granules on whatever litter you already buy, mix gently, top up when the box gives off a smell again. The active ingredient is filtration-grade activated carbon. Not perfume. Not sodium bicarbonate. You also get to keep the litter you actually like.

Different category, same shelf budget, better chemistry.