It seems all but impossible to fully "ban" second hand smoke: * how do you prove it? * how do you measure the amount in case you've proven it? It seems such a minor individual offense that courts would hardly accept cases.

So we probably have to rely on smoker's good will to not smoke near others instead of on the law.

Every population consists of nice people and inconsiderate people, with something like a normal distribution of niceness. Assuming that smokers follow this distribution, there will always be inconsiderate smokers which don't care and stand in front of doors blowing clouds of tar into other people's faces. The amount of such people will be governed by the rate of smokers. Hence, the best way to reduce second hand smoke is to reduce the count of smokers. Note that this even applies if we assume that smokers are much more considerate than the regular population.