Doesn't matter if they say they smoked or not there is a noxious odor that needs to be treated. 

Hello everybody,   I know someone on here had to remove pet odor from their carpets, I have a rental where I had my carpets professional shampoo cleaned but it still smells like pets were there.   

Watch a nice person turn foul mouthed and angry instantly.

I'd have them pay a non refundable pet fee too (~$500 depending on the dog and cost of remediation in your area) to take care of any carpet cleaning and odor removal you may need to do after they leave.I'm also concerned about having a couple in the house.

I recommend using an Ozone machine for all smoke odors, just read the instructions and be mindful of the safety concerns when using Ozone.

If there is any odor after professionally cleaning them, then I will replace them and deduct from deposit.  

The pet odor was stronger than before.

I went to work with a strong nicotine odor embedded in my clothing.

A reputable carpet cleaner told me today that there's nothing he can do to reduce the odor.

Spent several days cleaning out the house (hoarding situation), did extensive odor remediation (cigarette smoke), and did some minor cosmetic updates.