Smoker husband

My hubby is a chain smoker and spend most of his time outside of the house smoking. I appreciate this as we have a 6mo old baby and a 3yo toddler inside of the house. He gets offended whenever I ask him about his smoking. I am worried about his health and also mine and my kids' health. My grand dad died of emphycema and I have asthma. Am I being selfish wanting him to quit? Any advise on how I can convince him to quit without offending him?