ALL of the aftermarket bumpers don't hurt the airbag deployment.

Air bags deploy if the decelleration is severe enough to hurt you badly enough when you are thrown forward.

So - If your BODY is going to keep going forward, relative to the interior cabin, with enough force to be of severe concern...the bag will go off.

___________________________________

Example - lets say you are in a battleship going 40 knots, and a 18' fishing boat crosses your path, and you hit it dead center, and cut it in half, etc...

Inside the battleship, you feel nothing...perhaps a slight knock, etc....but, your momentum carries you forward, and the battleship's decelleration in response to the impact is negligable...

...An airbag, if the battleship had them, would not go off, as you didn't decellerate enough to set it off....you did not NEED the protection.

____________________________________________________

If you do the same thing in your 12' motor boat, and hit the 18' fishing boat at 40 knots the same way...you WILL decellerate noticeably...and, if you HAD airbags, they might go off.

_____________________________________________________

If you repeat the experiement on the road....lets say with a shrock...

You plow into a car, and the momentum of your truck carries you through, so you are still going forward...and the other car is pushed back...the energy is transferred to the other car...and you don't get decellerated as much.

Without the shrock...assuming the impact is about the same...the same thing would happen, except you'd have more damage, and your truck's bumper would do more crumpling.

If you hit a tree, or a rock, etc...YOU do all of the absorbing and decelleration will be from whatever to 0, assuming the tree/rock doesn't budge.

____________________________________________________

So - the bumper doesn't really change the momentum, just the transfer, as the OTHER rig has to absorb the damage, and YOU get to carry forward intact.

If the crash was severe enough to crumple your frame, that will still happen, as the bumpers are merely mounted to the frame horns out in front...

The bumper will DISTRIBUTE the impact across its face though, lessening the severity, and providing more structural integrity...and ultimately, subjecting the truck to less stress.

(An impact that is not distributed tends to cause the most damage...a driver's side head light to passenger's side headlight type collision is more severe than a grill to grill head on crash for that specific reason....and why European crash tests are offset crashes, etc.)

----------------------------------

Several people have reported collisions that they survived BECAUSE of their bumpers, ARB, Calmini, Shrock for example...ALL have examples of taking the hit and saving the X....mostly by DISTRIBUTING the force across the face of the bumper.

Sometimes the airbags go off, if needed due to the rate of decelleration, and sometimes they don't, because they were not needed. (In all cases, the bags worked when they were needed/properly).