Exeng, aside from the fact that the whole "passive smoking" health risk myth has been thoroughly debunked by several studies (including one released last year by the World Health Organization), the fact is that if A/C ventilation standards were set to a reasonable level then there'd be no reason for any non-smoking pax to be exposed. Correct me if I'm wrong, but don't all aircraft send fresh air into the front of the cabin and exhaust it out the back? If that's the case, then a reasonable flow rate and a smoking section in the back shouldn't be a problem.