Can you extinguish a flame without touching it? This fun classic science activity is always a crowd pleaser. Carbon dioxide is heavier than air, so when it’s released near a candle, it replaces the air (which contains the oxygen needed for fire to burn) and puts out the flames!
WARNING – This activity involves fire and should be supervised or performed by adults
There are two easy ways to create enough CO2 to put out a small flame. You can create it with a baking soda and vinegar reaction or collect CO2 in a balloon placed on top of a bottle of fizzy water.
Collect Carbon Dioxide Using Carbonated Water
Simply place a balloon quickly on a bottle of fizzy water when it’s first opened. If you swirl and gently shake the bottle, the CO2 will collect in the balloon and inflate it.
You’ll need
An unopened bottle of fizzy water ( club soda or sparkling water )
Balloon
Tea light candles
Matches or a lighter
Heatproof surface
Instructions
Place the tea light on a heatproof surface and light it.
Remove the lid from the carbonated water bottle and quickly place the balloon over the opening.
Gently swirl and shake the bottle to release the trapped gas. You’ll see the bubbles rising, and the balloon will start to inflate.
Once the balloon stops inflating, carefully remove it from the bottle, pinching the end so no gas escapes.
Hold the balloon over the tea light and slowly release the carbon dioxide. The tea light should go out.
Collect Carbon Dioxide with Bicarbonate of Soda and Vinegar
Carbon dioxide is released when vinegar and bicarbonate of soda react.
You’ll need
Tea candles
Matches
1 tablespoon of bicarbonate of soda
100ml vinegar
A medium sized jug
Instructions
Place the tea light on a heatproof surface and light it.
Pour the vinegar into the jug and then add the bicarbonate of soda. You should see bubbles of gas (carbon dioxide) straight away.
Carefully tilt the jug over the tea light so the CO2 is near the flame. It should go out!
Where are CO2 fire extinguishers used?
CO2 fire extinguishers are used for electrical fires. Fire needs oxygen to burn, but when carbon dioxide is sprayed over the fire, it covers the flames in a blanket of carbon dioxide, which starves the fire of oxygen and puts it out.
One advantage of using CO2 is that it doesn’t damage expensive equipment like water or foam.
Fun Fact
When CO2 gas shoots out of a fire extinguisher, it’s so cold that it can turn into ice crystals.
Last Updated on October 14, 2026 by Emma Vanstone
