Hyundai Elantra: Why didnt my air bag go off in a collision? (Inflation and non-inflation conditions 
of the air bag) - Air bag - advanced supplemental restraint system - Safety features of your vehicle - Hyundai Elantra MD 2010-2015 Owners manualHyundai Elantra: Why didnt my air bag go off in a collision? (Inflation and non-inflation conditions of the air bag)

There are many types of accidents in which the air bag would not be expected to provide additional protection.

These include rear impacts, second or third collisions in multiple impact accidents, as well as low speed impacts. In other words, just because your vehicle is damaged and even if it is totally unusable, dont be surprised that the air bags did not inflate.