The Powerpack grants its wearer multiple buffs while worn. It does the following:
Reduces recoil on ground, and no recoil while climbing - This allows the Spelunker to fire their weapon such as the Shotgun without being pushed back much or at all. This does, however, prevent the player from 'gun-jumping'.
The Powerpack will also increase the radius of the explosion of your bombs, and make them slightly bigger as a visual indicator.
The Powerpack is a pack, so it will explode if catches fire from things like torches, shotgun pellets (very briefly), Magmars, being near Lava, etc. The explosion deals 10 Health Points of damage to you, or anything else around it.