When you think of bees and honey you may picture a beekeeper in one of those full body suits, removing the lid from a hive and pumping smoke into it. While it is common knowledge that the smoke calms the bees down, it is lesser known as to why this is the case.
Normally, when the guard bees detect an intruder they release a pheromone into the air called isopentyl acetate. This alerts the other bees to attack and protect the hive. When the bees are smoked, however, the process of releasing the pheromone is interrupted and no bees get the alert that the hive is at risk.
The smoke also has the effect of making the bees eat the honey in the event that they will have to move and rebuild the hive due to fire. The consumption of honey makes the bees subdued and less aggressive.
The combination of these two effects allows a beekeeper to do what he or she needs to do in the hive without the nuisance of being attacked in the process. And in case you were wondering, the smoke does not harm the bees in any way.