If you really want to start a war, go to cruiscritics.com and post this question in the Carnival forum,,you will see a fun war break out.
I have never been on a Carnival ship yet,,will be soon,, but I have sailed on Holland America 4 times. They have the same basic policies as CCL which is that smoking is allowed in all staterooms, there are no non-smoking cabins. But I will also share this. On one of my cruises on HAL I stepped into my stateroom and almost passed out from the stale smoke smell. I asked my cabin steward if anything could be done. He asked what I was doing and I told him I was going to lunch (this was obviously during embarkation) and he told me he would take care of it. After lunch we returned to our cabin and it was a fresh as a daisy. I think they have some kind of heavy duty atomizers and room freshners that can take out the smell.
On the cruise critics forum I have read people saying that they did have smelly cabins and that Carnival was able to freshen the rooms for them. but some still bring that Febreeze stuff with them, jsut to be sure.