How do I get rid of cigarette smell coming from somewhere else?

Gabriela • First time mom. 23. Due 06.26.17
I am 19 weeks pregnant and live in an apartment, and on an off their is this strong smell coming from the living room.
What can I do? 
My window isn't open
The heater is independent and their are no vents
Is it possible that perhaps someone who lived here years ago, who was a smoker the smell be lingering still? 
Please help! Thanks :)