What can I use to remove this awful smoke smell??

Gabriela • First time mom. 23. Due 06.26.17
I'm 20 weeks pregnant and the apartment I am currently living in, had someone who was a smoker and a section of the living room area smells strongly of cigarettes. Like if someone was smoking there, even though the person who use to live here did so years ago. 
Please what can I buy online to remove this horrible smell??? 
It is not all the time that it smells like this, but on and off. 
Thanks!