This will likely be an expensive research project as it might require obtaining lung tissue contaminants and matching them to the residue in your home.  

I have now restricted the rental to just one person for the foreseeable future.INFO: 4 months left on the lease and almost all of one floor turned out to be sprayed and urine contaminated.

Maintenance costs will also be higher here due to the salt contamination. 

Like a couple years ago when we were building  an addition and found contaminated soil and an abandoned oil tank .  

We are surrounded by superfund sites, and every stream I've found has warnings about contamination.  

This will avoid contaminating all of your businesses with "dealer status".Dealer status may also apply to operating as a sole proprietorship (buying/selling in your personal name), so be careful and get expert tax advice.I am not a lawyer or accountant, so ignore everything I just said and get your own professional advisor.

Another problem you could end up with is, by introducing alot of fresh water the system could become contaminated if your boiler water is treated.

Let's say you get your way, that anything goes as you believe so long as it doesn't "hurt" anyone else.That would mean you can have a tenant that puts on the red light and has strangers over at all hours going through your building, that would be okay so long as they were quiet and didn't hurt anyone.It also means that your tenants could legally sit inside and smoke crack, getting high and contaminating the unit, after all, it would be perfectly leagl.

Unless you are trained and certified in safe remediation techniques, taking your own measurements with a moisture meter is pretty useless and self diagnosis and removal of materials that are suspected to be contaminated is a bad idea.

Have a professional cleaning crew clean up the crime scene area, contaminated rooms, just as an added piece of mind for the new owners.