The non-toxic, natural cleaning powers of baking soda have been known for generations, and one of the most common uses seems to be leaving an opened box of the stuff in a refrigerator, with the goal of combating odors. Many people leave the same box of baking soda in the fridge for months or even years, so we wondered how well this really works, and if there might be something better.
In response to a reader question posed to the Argonne National Laboratory outside Chicago, a "ProfHoff" wrote that leaving a box of baking soda in the fridge to soak up odors "does not work very well." The post explained, "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[d] lose a great deal of its already limited surface activity." Instead, Hoff suggests using activated carbon.
On the other hand, the science advisory board of The Straight Dope confirms that baking soda, which is really sodium bicarbonate, can in fact neutralize strong acids and stabilize strong bases. That's significant because, according to the scientists, a bad odor "is almost always the result of strong acids (in the fridge, often lactic acids) or bases (found in spoiled meats)."
Still, exactly how effective baking soda is in removing odors from refrigerators in the real world is unknown. "We don't know of any studies that have looked at that, it's only anecdotal evidence," said Leslie Stein, PhD, the communications director for the Monell Chemical Senses Center in Philadelphia.
So, there are no objective studies that could suggest whether activated carbon or another material would be more effective at removing odors. We asked Carolyn E. Forte, director of home appliances and cleaning products for the Good Housekeeping Research Institute, what she recommends. "We have never tested the performance of baking soda vs. activated charcoal, but activated charcoal is a known odor absorber," said Forte. "[Contributor] Heloise has recommended it quite often and for the refrigerator when odors are particularly bad. Baking soda does work, but I think activated charcoal is available in pet supply stores, so my guess it that it is better suited for stronger smells."
In fact, activated carbon is what's used in many water and air filters, both in industrial applications and in consumer products like pitcher and faucet filters, air masks and aquarium filters. Activated carbon is also used as an odor-busting additive in cat litter. The material is sometimes called "activated charcoal" because it's commonly produced from charcoal. The source carbon is treated by one of several industrial processes to make it extremely porous (aka "activated), so it can absorb and bind a high amount of odors or contaminants.
We called up an activated carbon importer and manufacturer to ask if he'd ever heard of using the material to remove odors from refrigerators. "I think activated carbon would work, it's just getting it to the consumer. You can already buy baking soda right off the shelf," said Spencer Pugh of Woodland Park, Colorado-based Winfield Industries. "Activated charcoal is more used in bulk, but that might be a good business for someone to get into."
The Daily Green spoke with Ray Brown, a research and development scientist with Church & Dwight Co., which manufacturers Arm & Hammer brand baking soda. Brown told us that his company is legally restricted from modifying the formula of baking soda or adding any additives (such as activated carbon) because the product is regulated as a food ingredient and pharmaceutical antacid. Brown said baking soda starts as ore mined from Wyoming, then has carbon dioxide bubbled through it, turning it into the useful sodium bicarbonate.
Brown said the way baking soda neutralizes odors is by turning them into crystalline salts, which don't give off any smell. These salts form the crust that develops on the top of the baking soda in the box in your fridge.
"We've looked at using other materials as deodorizers, such as activated carbon and zeolites, and they have their pluses and minuses," said Brown. "Whereas baking soda is selective in how it works, neutralizing acids and bases, activated carbon is very broad, absorbing virtually all odors, including the neutral ones we generally find pleasant, such as floral and fruity odors," he added. Brown said activated carbon can begin to release the odors it absorbed if it becomes saturated, or if the temperature increases even a few degrees. "We didn't find that activated carbon improves the performance that much, and baking soda is a very effective deodorizer in the fridge or freezer," he said.
Baking soda is also substantially cheaper than activated carbon and more familiar and widely available. A nine-pound bucket of activated carbon costs about $50, whereas a 13.5-pound bag of Arm & Hammer baking soda costs about $14.
Tips for Better Odor Removal
Church & Dwight recommends putting a fresh box of baking soda in the fridge every 30 days. "The key is to get the baking soda in contact with the odors," explained Brown. "Baking soda is not like a fragrance, which goes into the air to cover up odors. Baking soda reacts with the bad odors. When the fridge door is closed, air is circulating past the baking soda, and odors are continually removed."
According to Brown, stirring up the baking soda in the box really doesn't help it work better. "That might give it a boost for a day or two, but not long term, because odors work their way through the whole box, not just on the top," he said. Brown added that the way to boost odor busting is to make sure airflow is not restricted around the baking soda box -- and yes, take the top off (or use an air filter product). Place the baking soda as close to the appliance's fan as possible. When you're ready to get a new box or filter, Brown says the used baking soda will still have enough power to use for cleaning counters, trash cans or drains, but don't use it for baking or personal care.
So what's the bottom line? There is solid evidence that baking soda helps eliminate odors, although its effectiveness does decrease over time. If you have a particularly nasty smell or want to get rid of a neutral odor like ripening fruit, you might try picking up some activated carbon from a pet store or online shop and using that as well. You could also try filling a thin sock with dry coffee grounds and tossing that inside, per a suggestion from Good Housekeeping.
What has worked best for you?
By the way, we followed up with Argonne labs, but the media manager of the U.S. Department of Energy-run institution, Steve McGregor, told us they didn't have any further details and they couldn't locate ProfHoff. When we pointed out an Internet search turned up a Robert Hoff working at Argonne as a systems administrator, McGregor said, "I'm certain he is not the same person."
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