Second hand smoke prevention

So my husband is Army and we just moved into this house less than a month ago (so moving out is not an option cause there is a lease). Neither my husband nor I smoke and do not want our baby around smoke. With that being said the more time we spend in this house we are picking up signs that the previous tenants smoked in the house. We have also been told that if the connected units have smokers inside the house it can transfer through the vents. Housing here has no rules against smoking in houses so I can’t ask my neighbors to not do it, it’s in their house and it’s not their fault these houses have crappy air vents that share smells from unit to unit. How can we prevent our little one from being exposed. Should I get an air purifier for his/her room. I have one in our room right now cause I’m highly allergic to cigarette smoke but I’m not really finding it super helpful.