There's no specific "speed threshold" for airbag deployment. What it ultimately comes down to a how abrupt the change in velocity is or "Delta V". If you're driving 100 and hit something causing you to slow down over the course of a mile the airbags are not deploying. However if you're driving 20 and stop instantly you're getting airbags.
Delta V is what it's all about, not the initial speed at impact. These systems have come a LONG way since airbags were fist introduced.
Ha ha, well that's pretty old school right there. The air bag sensors in the bumper are about 20+ years old. Modern airbags are controlled by the ACM (Airbag Control Module) which is typically located somewhere near the vehicle's center of mass, so you're not going to find any sensors under your truck. This module measures speed, braking, steering inputs, seat belt status (on/off) Delta V, yaw, pitch, roll and a whole slew of other items. The readings are monitored and processed in milliseconds the entire time you're driving. If all this data says you're in danger of injury, the air bags go off. That's obviously a simplified version of it but that's the gist.
Not to worry though, "big brother" isn't watching everything you do. All of that data is recorded, but it's like a dvr. If the event isn't locked/saved, it will be overwritten. Some event's are locked some are not. Air bag deployment events are always locked, although looking at the image posted I suspect this was a locked even too.
Technically speaking if you're driving down the road, and hit a pot hole, you could read the data which will show that pot hole contact. That's not a serious enough event to lock the data so it will be overwritten by the next event (although some ACM's store 2 events so you may need 2 following events to erase the pot hole).
OP, did they happen to give you a pdf of the data? I'd be happy to look at and let you know what I see if they did.
