I would suggest he stays away from her period when he smokes. Even third hand smoke in fabric and drywall is showing up as dangerous in tests now. Lung cancer is no joke and can come from 2nd and 3rd hand- my dad died from it recently and It's a horrible death with far fewer treatment options than many other cancers.
Its because the nicotine sticks to your skin and is toxic to young children. In extreme cases infants can get sick or even die. :\ Not trying to freak you out, its just what I've read\heard.
I'm not sure how it is in every state, but I know here they just passed a bill stating you can't smoke in a car with children under 16. If a cop sees it they can pull you over and ticket you for it. But as far as just around children in general, I've never heard of that