On sensing a collision an airbag will deploy in an average of just 30 milliseconds.
An airbag depoys when a hard impact its the vehicle and the airbag automatically deploy's before the driver and passengers hit the front of the car/seat.
Possible clockspring failure.
it will deploy if hit hard enough.
It is suppose to deploy in a frontal crash
No an airbag will not deploy if the battery is disconnected
The airbag system has a malfunction and will not deploy if needed as long as the airbag symbol stays on.
Once
If the car is off and no one hits you the airbag should not deploy. If you are driving and stopped at a traffic light and someone hits you, the airbag could possibly deploy depending on the impact of the accident.
200 mph
It's most likely a broken clock spring. Does your horn work? If it doesn't, it's most definitely the clock spring. It's behind the airbag. From what I've been told, the airbag won't deploy, even in an accident.
You need to have someone with a scan tool check the airbag system for trouble codes. The airbag system is not a place for do it your selfers.