The odor stays there for years.

You need to get inside the unit to determine if the smoke odor is found within.

@Joshua Strong It's hard to say without knowing exactly what's going in there.I'd talk to the town zoning board to see if they can give you any insight - but remember that they can change the rules at any time.That said, I'd expect that anything that create more traffic (especially loud traffic like tractor trailers), noise, odors, air pollution, etc will drive down property values.  

I've been fairly lucky, foul cooking odors and cigarette burnt carpets biggest headaches.

There are some paint strippers that are non-flammable and odor free.

So with the balloon experience in hand, maybe that smell isn’t stale, rather it has kept it’s odor fidelity all these years!

Smells and odors, especially urine. 

Residents who wish to be "grandfathered" and continue smoking will be allowed to do so; however, if odors from someone's smoking can be detected in another unit or common area, then the Board can permanently remove the "grandfathered" exception for that owner.  

Hire a company that has special services for pet staining and pet odor and deduct from the deposit at the end.In my opinion a pet fee does not cover damage to the property.  

We're looking at buying an ozone machine to help with odors after tenants vacate.