When fermenting peppers, or any other food or drink, there's a small risk that your mason jar or bottle may explode. That's because carbon dioxide is a natural byproduct of fermentation. If you're fermenting in a tightly sealed container, the carbon dioxide has nowhere to go and will build up in the jar, potentially leading to cracked, seeping, or (rarely) exploding jars. To prevent your jar from exploding, use an airlock when fermenting. Lids that are designed for fermentation allow carbon dioxide to escape, so there's no risk of cracked or exploding jars.