The combustion is a result of the reaction of the oxygen with other substances. The usual extinguisher works removing one of the essential ingredients for the combustion - the oxygen. In the present experiment, the reaction between the sodium bicarbonate and the acetic acid (vinegar) produces carbon dioxide. The carbon dioxide is a colorless gas, with no smell and denser than air. As the carbon dioxide forms, it starts to occupy the bottom of the jar. In a certain instant, the level of carbon dioxide passes the height of the smallest candle, leaving not enough oxygen for the combustion, extinguishing it. After, the carbon dioxide level increases and reaches the height of the bigger candle, extinguishing it equally.