Alseire,
The smoking area airside in Dublin is in Terminal 1. It's just off the bar/restaurant that is beside Burgerking in the shopping area and is well signposted. It is a nice big area and you see a lot of staff there as well as passengers there. There is a good ammount of seating there.
It's strange that T1 was adapted to include a smoking area while T2, a new build, was built without one. I have gone to the smoking area as a passenger in T2 but you do need to have a bit of time on your side.
The first smoking area in Ireland was in Shannon. I read that it was developed to facilitate the American soldiers transiting from Iraq/Afghanistan passing through there