There are many dangers that can come from a person smoking. These include lung cancer, heart disease, stroke, cancer, cell damage, and many others
Sources
Secondhand Tobacco Smoke or environmental tobacco smoke (ETS)
This type of smoke is a mix of the smoke emitted and the smoke inhaled by a person. STS can cause lung cancer and many other diseases in the body. It has the power to move very quickly between different rooms in a home. This means anyone can be affected by just the smell alone
How to Limit & Avoid an Indoor Gas Danger
Secondhand Tobacco Smoke
To limit the danger (not completely eliminate it), be sure to ventilate the area where you are smoking and do it outside rather than inside. Also, do not smoke around younger kids as it can effect them more than it would an older individual.