Passive smoking: 600,000 people affected anually

First Global study found, it causes 600,000 deaths every year. One-third of those are children, often exposed to smoke at home. It is really dangerous for children, it has higher risk of sudden infant death syndrome, pneumonia, asthma, respiratory illness & it causes lungs cancer. Any person exposed to passive smoking may experience short-term symptoms such as a headache, a cough, wheezing, an eye irritation, a sore throat, nausea or dizziness. Adults with asthma may also experience a significant decline in lung function when exposed to secondhand smoke. Under these conditions it can take as little as half an hour for an individual's coronary blood flow to become reduced.

In my opinion people who smoke does keep it under the exposure of others because second hand smoke or passive smoking is more harmful as compared to direct smoking. It is fine until you keep your insanity up to yourself and not damaging others with the smoke you exhale. Smoking is haram because it damages one from inside, produces pollution & cause diseases among people around you, if one can not stop it it must avoid smoking at public places or in transport.