New York Times on ETS in multifamily housing

A recent article in the New
York Times
focused on the problem of cigarette smoke drifting between units in apartments and condominiums. The second paragraph highlights recent ordinances in California. The only mention of exposure potential is this:

Researchers have analyzed whether smoke can be contained in various kinds of apartment buildings and found that the percentage of shared air generally ranges from 10 percent to 50 percent, with upper floors most at risk...

I've had many people calling to find out how they can demonstrate that ETS is entering their apartments. In one case a retailer next to a tobacco shop was inundated with cigar smoke and needed to figure out how to prove there was a problem.

Practical advice or Fact Sheets focusing on exposure science in this area are needed.