Baking soda Uses neutralizes odor by turning them into inert crystalline salts over time. That’s what the crust is over the top of the baking soda in the fridge etc. Changing the box frequently is best (every 1-3 months), you can then use the baking soda when making basic home cleaning solutions to clean sinks, counters or garbage cans etc. My favorite is the sink, and kitchen garbage can. That way I know I am keeping up on some of the detailed kitchen cleaning by giving my kitchen garbage can and stainless steel sink a through cleaning once a month when a change the baking soda in the fridge.