Remember Legionnaire's Disease?
 

The news at the time said it was in the air conditioning ducts. False. It was in the coils.

https://www.youtube.com/watch?v=aN_pdTYwE_8

This is excerpted from a hour and twenty minute interview at Disruptive Investing.

10% of energy consumed worldwide is for air conditioning. That could be cut in half and improve the health of people in hospitals and grade schools (the worst places).

Automobile air conditioners are a difficult case.