Carnival has pretty consistant designated smoking areas....but here lately some of the newer ships have had some changes.
For the Sensation, most of the designated space listed previously will be on Promenade. (casino, cover band bar, disco and cigar bar)
The piano bar is on Atlantic next to the middle Main Dining Room.
Then out by the pool on the Starboard side.
And of course, on your balcony.
The only thing to remember is that walking from venue to venue with a lit cigarette is not allowed. And if someone smokes in their cabin, they can't prop the door open, since there is no smoking allowed out in the hallways.
Thanks for checking where smoking is allowed, as a nonsmoker, I always appreciate courteous smokers.
Another note, I have friends who use the electronic cigarettes when they are on a cruise. You can use these ANYWHERE at anytime, but you will get questioned from time to time by staff until they realize it is an E cig...
Have a WONDERFUL cruise!!