I'm trying to think of a solution involving fans or blowers, perhaps combined with a cigarette smoke detector to automatically activate fans that blow the smoke back towards the offenders. It's probably a 10 foot distance between the decks.
This shows a similar pair of townhouse units and the problem: < http://oi42.tinypic.com/1608l8j.jpg
I'm thinking about this unit: < http://www.vproducts.com/p-secondhand-smokedetector90.htm model 9040 connected to a large fan, i.e <http://www.northerntool.com/shop/tools/product_200460841_200460841>. I'd need to shield it all from weather somehow though the tenants could bring it in if it's raining hard so just an outdoor umbrella would suffice.
Any other ideas for blowing the smoke back?