Prophet Muhammad (PBUH) narrated in a famous hadith “when Ramadan comes the gates of Paradise are opened and the gates of Hell are closed and the shayateen are chained up.” This hadith is reported in Bukhari and Muslim.
This is the mercy of Ramadan that the doors of Paradise are opened wide and the doors of Hell are tightly closed. The shayateen are chained causes a lot of confusion for many people.
Many believe the large shayateen are chained but the smaller ones are still around. Whatever this meaning we know that the influence of the shyateen is much smaller than any other time of year.