We keep a small box of baking soda in the refrigerator and another one in the freezer. We try to use the special "Fridge and Freezer" packages of baking soda. These packages are designed to allow for better air flow. Better yet: since these special packs of baking soda don't need to be ripped open at the top, they can't spill when you're reaching into the deepest corner of your freezer searching for a long lost Klondike bar.
Arm and Hammer says baking soda used to keep the fridge and freezer smelling fresh should be replaced every three months. (This is pretty obvious, but don't even think about using the baking soda from the fridge in your next batch of Irish soda bread. The baking soda will transfer those off odors and flavors to your food.)
The August issue of Real Simple magazine suggests another cure for smell that baking soda can't cure: the Fresh-N-Cold food preserver. This $30 gadget can be revitalized monthly for one year, by sitting it in the sun for 4-5 hours.
Buyer Beware: Consider potential odor problems the next time you shop for a refrigerator. Our old fridge never had this problem the way our new bargain model does.