2016 has not been a favorable year for airbags. Some deploy with too much force. Some don’t deploy during crashes. And then some, like those in the 2016 Prius, can deploy at any random time — even if the car is parked, turned off, and unoccupied.
“The front passenger airbags contain compressed gas that is stored in the inflators. Toyota didn’t go into many details, but a component inside the airbag might not have been welded correctly during assembly. The stored gas can escape from the inflator and cause the frontal passenger airbag to deploy without warning.”
Toyota expects to start sending notices in November 2016.