The one I am thinking of involved a resident dying  because another resident was drunk and his lit cigarette was disposed of such that it set the place on fire.

Convicted felons and smokers both fall into the same category of not being a protected class correct? 

Some behavior you want to exclude right off the bat for sure - smokers, etc - and I don't disagree with your premise that I don't think I'd want that situation under my own roof - but if a person is not breaking any law, you have to either let them do what they want within reason or let them seek accomodations elsewhere.

Now that they are gone (strange folks), there is severe cigarette smoke odor concentrated in one of the 2nd floor bedrooms, also affecting the hallway.

Decide what you're willing to compromise on-- renting to pets, smokers, students, bad credit, or what?

Right, I'm referring to minimum credit score, 3x monthly rent income requirement, non smoker.

I used that to get cigarette smells out of my leather seats in my car, and it worked wonders.Coffee grounds can also work in a similar fashion.Also, open the windows and bring in some big box fans.  

I don't allow smokers period so I don't think I could comment.

In reality I would treat it as if you were to treat cigarette smoke residue.  

In your country, anything over 4-5 PCi/L usually comes with a recommendation to vent the radon to the atmosphere external to the building envelope.  30 PCi/L would present a high risk factor towards developing {lung} cancer {particularly among smokers}.