Pipe tobacco different than cigarette tobacco?

[aeropl]

Why is it that the second hand smoke of pipes usually smell very sweet and 'smooth', while second-hand smoke from cigarettes is not pleasant at all? That's my opinon obviously but I think most people would agree there is a difference. So my question is, why is there such a difference in the different types of smoke from different means of smoking tobacco? Do pipe users use a different type of tobacco, or is it processed differently than cigarette or a cigar?

Also, we've all heard about all the bad chemicals that are in cigarettes (ammonia, cyanide, etc). Are these chemicals in the tobacco naturally or are they added by the cigarette makers? If so, why would they add these things? I'm thinking this might contribute to the difference between the smell of cigar/cigarette/pipe smoke.