And I'm sure there are more synthetic opioids coming: we've only known about fentanyl since the 1950s and carfentanil since 1974.We're talking about tiny, tiny amounts of the target substance here.

https://www.drugs.com/medical-...In 2020, there were 56,000 overdose deaths due to synthetic opioids like fentanyl.

From building code violations leading to extreme damages, or injury, or death, and mold, asbestos, hazardous chemicals/substances found on site, etc.   

If there is a serious earthquake, hurricane, city wide fire, tornado, hail storm, flood, chemical spill into the water supply, crime increase, riots, drug house down the street - I know that these never happen, (except that these are rather regular occurrences) but let's say such an occurrence occurs in your neighborhood, what do you do if you own?

The water tends to have a chemical taste and smell.

Two treatment options:1) They put chemical into the effected areas through holes in the sheetrock.

My thoughts would be chemical, even though that will likely kill it back to the roots, on their side (oh well!).

They start diluting the (expensive) chemicals, and tenants complain that the bugs are out of control. 

We recently turned over one managed unit ourselves and sprayed chemicals, round up and home pest control, right before we left.  

Smoke alarms down like the fumes the Zinsser Shellac gives off so remove them before you apply the shellac so their sensors don't get saturated with the chemical.