Monday February 19, 2018 Q&A

How does baking soda get rid of bad smells?


1 It traps the foul-smelling molecules

2 It releases a neutral odor that covers up the bad smell

3 It's a myth – it doesn't get rid of smells

Correct answer: It traps the foul-smelling molecules.

Baking soda is often described as a natural miracle product. Putting a bowl of this unassuming white powder in your fridge is supposed to rid it of any bad smells. But does this really work? We spoke with EPFL chemist Kevin Sivula to find out.

Baking soda is the common name given to sodium bicarbonate (NaHCO3), which is composed of sodium and hydrogen carbonate. It is a weak base with amphoteric properties, which means it can behave like either an acid or a base depending on the compounds it comes into contact with. So it can indeed neutralize unwanted odors. 

© iStockphotos

In a fridge, bad smells come from the volatile gas compounds that are released from food and make their way through the air to our noses. If they come into contact with baking soda, a chemical reaction takes place. The two molecules bind together, which neutralizes the smell – and it doesn't matter whether the odor comes from something acidic, like cheese or vinegar, or from something alkaline, like garlic. 

If there's enough baking soda to bind with all the volatile molecules in the fridge, the bad smell will be totally neutralized. However, once all the baking soda particles have been saturated, no more molecules can be absorbed. Other natural substances, such as coffee grounds and activated carbon, also produce the same deodorizing effect. 

A well-known property

Researchers in Malaysia have studied the effectiveness of baking soda in neutralizing the smells coming from organic waste. They found that 50 grams of this powder spread across the bottom of an eight-liter garbage can containing food waste can reduce the smell by around 70%. It also prevents bacteria from growing.

For more information: 
Preliminary observation on the effect of baking soda volume on controlling odour from discarded organic waste, Qamaruz-Zaman N. et al. Waste Manag. 2015 Jan; 35:187-90. doi: 10.1016/j.wasman.2014.09.017. Epub 2014 Oct 18.

Thanks to Kevin Sivula from EPFL's Laboratory for Molecular Engineering of Optoelectronic Nanomaterials