DS is 3 and always comes home reeking of fags. I know ex smokes in the car and at home he sits on the backstep with the door open (whilst DS is obviously in the room too as he's keeping an eye on him at the same time).
I've asked a few times (his sister let slip he still smokes/smokes in those places) and he denies it everytime so how would you go about getting it to stop.
DS said 'mummy, stay there, i'm going for a cigarette' the other day 
Not sure why but it made me so sad. I don't want him thinking it's a good option/being set that example.
Stupidest thing is that ex's dad died at 49 of a heart attack and smoked like a chimney despite being very 'healthy' in all other ways.