Ethlene

Ethlene gas is a flammable organic compound; it's actually the most heavily used organic compound in chemical industries worldwide. It's also an important plant hormone that is responsible for the ripening process in all fruits.

When a fruit is ready to ripen, it releases this hormone in preparation for a) reproduction and b) decomposition. All fruits are put in two categories according to how they react to ethylene gas: climacteric fruits, which react to ethylene in their environment by hastening the ripening process, and non-climacteric fruits, which do not ripen as a response to outside ethylene. This is the reason bananas continue to ripen on the counter, but berries such as grapes and blueberries do not. Regardless, all fruits produce ethlene when it's the optimal time to reproduce.

Food warehouses take advantage of this process by exposing fruits to ethlene on purpose right before selling them to supermarkets. This means farmers can pick certain fruits when they are unripe and firmer, making shipping safer.

However, this is not without its dangers. Ethlene gas is extremely flammable, and fruit storage explosions have actually killed people.

https://www.npr.org/sections/thesalt/2018/09/24/650585212/science-reveals-how-fruit-keeps-a-lid-on-ripening-until-the-time-is-right
https://extension.umd.edu/resource/ethylene-and-regulation-fruit-ripening
https://en.wikipedia.org/wiki/Ethylene