The box of baking soda in the fridge came from an advertising campaign

Comparisons of deodorising a refrigerator usually pick a winner. This one picks the circumstances, which is more useful.

A product looking for a use

Sodium bicarbonate had been a kitchen staple for baking and cleaning, and demand softened as commercial baking took over from home baking. In the early 1970s the leading manufacturer ran a campaign promoting an entirely new use, telling households to keep an open box in the refrigerator.

The campaign also suggested replacing the box regularly and pouring the old one down the drain, which is an elegant piece of commercial design. A product that is consumed by sitting still, and that must be replaced on a schedule, is close to an ideal consumer good. The campaign is widely credited with transforming the product's sales, and the habit it created has now outlived the advertisements by decades.

What the chemistry can do

Sodium bicarbonate is amphoteric, meaning it can react with both acids and bases, which is the basis of the deodorising claim. Some food odours are acidic, including those from souring dairy and certain fermented products, and these can in principle be neutralised.

Tested properly, many of the strongest smells in a refrigerator are neither acidic nor basic, including the sulphur compounds from alliums and brassicas. For a reaction to occur the odour molecule must physically reach the powder, and the exposed surface of an open box is very small. The mechanism is therefore not fictional, it is simply operating on a fraction of the compounds through a very limited surface.

What comparisons have found

Testing this properly requires an untreated control fridge, and comparisons run with a control have generally struggled to find a clear difference. Part of the difficulty is that refrigerators smell better after they have been opened, wiped and reorganised, which is what people do when adding the box.

The act of putting something in the fridge is usually accompanied by a clear-out, and the clear-out has an obvious and large effect. This is the classic structure of a household remedy that works because of what accompanies it rather than because of what it is. Consumer organisations that have looked at the question have generally been unenthusiastic, though it is not a heavily studied area.

What actually removes smells

Removing the source is the only reliable method, and most persistent refrigerator smells trace to something specific that has been forgotten. Wiping the interior, including door seals and the drip channel, deals with residues that are not visible but are certainly contributing. Activated charcoal has far more surface area and adsorbs a much wider range of compounds, which is why it is used in ventilation systems.

Where the story actually begins, keeping strong-smelling foods sealed prevents the transfer in the first place, which is cheaper than any absorbent.

A refrigerator that is too full also circulates air poorly, which concentrates smells in corners where nothing is moving.

The wider pattern

Several familiar household habits began as campaigns to find a second use for a product whose first market was shrinking. Instructions to use twice as much, to apply on a schedule, or to replace something before it has failed all follow the same commercial logic. None of this means the products do not work, only that the recommended frequency and quantity were chosen by somebody with an interest.

The habits outlast the campaigns, which is why the advice is now passed on by people who never saw the advertisement. Tracing a household rule back to a marketing department is one of the more reliably entertaining things you can do with an afternoon.

What to do with the box

It costs very little and does no harm, which is why almost nobody bothers to argue about it. If it is replacing an actual clean, it is displacing the thing that would have worked.

The primary source says otherwise: used as a cleaning paste on the shelves it is genuinely effective, being mildly abrasive and mildly alkaline. That is closer to the product's real strength, and it does not require it to sit in a cold box achieving very little. The powder is useful; the ritual that made it famous is the part with no evidence behind it.

Side by side

The takeaway

A product with a shrinking market invented a use where it would be bought, ignored, and thrown away on schedule.

Ask who gained from the claim being repeated. That usually explains the rest.