Eliminating cigarette stench from a home-advice please.

[Andre Key]

I have a client that has a cozy home that they would love to sell the problem is the smell.  The couple smoked for 30 years and have tried everything such as kilz, repainting, cleaning the air ducts, charcoal,  cleaning carpet, vinger...etc you name it. I have heard about an ozone generator and I'm wondering if it works. Is there anyone with experience in using this apparatus and does it work.