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I have always been told that an open box of baking soda will "absorb" odors and make a fridge smell less. I have even seen people with three boxes in one fridge. My question is whether there is any scientific evidence for this claim.

It seems entirely possible that it is purely confirmation bias; the boxes are always installed at the start of a keeping-the-fridge-decent campaign.

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Well I don't know if it works in the refrigerator but I can guarantee that it will work on smelly shoes. I had a pair of workboots that got really wet. I left them to dry for about a week. When I next wore the boots my feet were totally stinking at the end of the day. The next morning I completely dosed them (about 3 tbsp in each boot). I wore my boots that day and at then end of the day there was no stink at all. I don't know how it worked but it did. –  user12106 Mar 26 '13 at 22:10
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The science behind the phenomenon is simply that sodium bicarbonate (as baking soda is known to its friends) is amphoteric; that is, it reacts with substances that have either strong acid or base pHs. Most things that we consider bad smelling in a refrigerator are giving off a vapor of strongly acidic particles, therefore sodium bicarbonate powder, with its large surface area, will react with those particles and neutralize them by making them less acidic. And of course Arm & Hammer will be only too happy to tell you all about this.

So it the science says it works in theory, but a better question might be, does it work really well? I found at least one chemist who doesn't think so:

The popular "open box of Arm & Hammer® in the refrigerator" simply provides an adsorbent material that can soak up odors -- but not very effectively. For example, if some of the odoriferous materials floating around in the refrigerator are acidic, the alkaline baking soda can absorb and neutralize the acid. Even in that regard, it is not all that effective because, as the powder in the box contacts water vapor, it tends to crust over an lose a great deal of its already limited surface activity.

He goes on to suggest using activated charcoal, though I would add that activated charcoal is much more expensive and should be disposed of more carefully. So while the baking soda may not work quite as well as advertised, it may still be the best option for most people.

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Thanks, how does one dispose activated charcoal? say I wish to recycle a used filter properly. Should not it be safe to just dump the carbon into the soil? –  Job Apr 27 '11 at 17:08
    
Hmm, good question. The activated charcoal things I've seen had scary looking stickers on them, but looking around the web it seems that the only important part is what they were used to absorb. (I worked in a plastics factory for a little while.) So if it's just in your fridge, I guess that isn't a problem. –  Scott Hamilton Apr 27 '11 at 17:36
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protected by Community Jul 19 '13 at 6:44

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