Best Air Purifiers for a smokers house?

My SIL is about to give birth, but she lives with her dad and his girlfriend who smoke indoors. She’s in high school, and I’ve tried to explain the risk of sids, but she doesn’t want to go anywhere else. I asked if I could get her an air purifier and she was up for that idea. I’m wondering what the best air purifier would be for a smokers house? I want to at least get one for her room where he will sleep. I wish I could afford to get one for each room.

Thanks!