CO2 Fire Extinguisher

Carbon dioxide extinguishes flames, but you've never put out a candle like this, before.

Carbon dioxide is a gas that we interact with every day. For instance, CO2 enables plants to perform photosynthesis, you exhale CO2 when you breathe, and CO2 can extinguish fire. You probably knew all those facts, but did you know that you can get really science-y and extremely creative when putting out flames with CO2? It's as simple as pouring the gas onto fire. Pouring? You better believe it!

Experiment Materials


  1. Pour some baking soda into a clear beaker or glass.
  2. Add some vinegar into the mix by pouring white vinegar into the same container as the baking soda. Whoa… that's a foamy reaction!
  3. Wait a few moments while the reaction tapers off.
  4. Use a lighter or matches to ignite the candle(s).
  5. Grab the container with what used to be vinegar and baking soda and slowly “pour” the air from the container. Be careful not to pour the liquid!
  6. As you move the container from candle to candle as you pour the air out, the flames will extinguish. No way!

How Does It Work?

Most flames require oxygen, fuel, and sufficient heat to ignite and stay lit. These three components of fire are referred to as the fire triangle or combustion triangle. Removal of any of the three components will cause the flame to extinguish or “go out.”

The secret to extinguishing fire is the removal of one of the three components. In CO2 Fire Extinguisher experiment, that lies in the bubbling mixture in the container. The baking soda (also known as sodium bicarbonate) is a base. The vinegar, or acetic acid, is a weak acid. When baking soda and vinegar are combined, the immediate acid-base reaction creates carbonic acid. Carbonic acid is unstable and decomposes into carbon dioxide (CO2) and water (H2O). The bubbling that you see inside of the container is the production of the CO2 gas. When you “pour out” the container, you're exposing the flame to concentrated CO2 gas. The lack of oxygen extinguishes the flame.

How can you possible pour a gas? The air that we breathe is comprised largely of nitrogen gas, a very light gas. The CO2 that was created inside of the cylinder is much heavier and, therefore, able to be poured like a liquid, out of the container.