Disclosed are devices and methods for treating tension pneumothorax. A needle assembly may include an outer cannula defining a lumen and having a distal end portion with a sharp bevel, and an inner cannula slidably-disposed through the lumen of the outer cannula. The inner cannula moves between an extended and retracted position and includes a blunt distal end portion configured to extend beyond the sharp bevel of the outer cannula when the inner cannula is in the extended position. The blunt distal end portion can retract within the lumen of the outer cannula when the inner cannula is in the retracted position, thereby exposing the sharp bevel. The needle assembly further includes a bias disposed inside the housing and coupled to the inner cannula. A proximal end portion of the inner cannula is configured to extend through the housing when the inner cannula is in the retracted position.