I used to be a smoker before I was pregnant. FYI, they do ban smoking but NOT all public areas. Most areas you mentioned are ok to smoke. As long as there is a rubbish bin with the "ash-tray" and as long as there is no "No Smoking" sign, smokers will just light their ciggies. And no offence, if you see ppl smoking, just walk away from them. They too have the right to be there just like you. It's all about tolerating one another. NEA officers are around just to make sure that smokers dont't litter in public and they dont't smoke at the restricted areas. Most NEA officers are wearing plain clothes so even if there's one standing beside you, you may not probably know.
But for your office, to be honest that's strictly a big NO to smoking, especially if it's an air-conditioned room. Just go to your boss and report the matter. If you dont't wish to be called a "snitch", then try talking to these ppl. Hopefully, they will understand your situation. I guess they're already trying to compromise by smoking in their own room and not near you. And if you really dont't have any options and you can't stand it anymore, get another job. Being in a stressful situation is not good for your baby either.