3rd hand smoke

Sa
Can someone tell me more about 3rd hand smoke
I use to smoke so I'm not judging but quit cuz we wanted to try for a baby. 
Anyway, my SIL has a new relationship and the SO is a big smoker and now my SIL is too! My SIL's SO got a hold of my son And ugh so stinky! My kid was just breathing in that nasty smoke smell. I'm sure we'll be fine this one time but I still worry. How long does it take for the chemicals to be outta my kid? I changed him and wiped him down with a cleansing clothe when I got him home. But I'm more concerned about him inhaling it. Signed,
super paranoid FTM afraid of SIDS