Abstract: The disclosure sets forth a breathing gas second stage regulator having a tilt valve for introducing breathing gas into a breathing box through means of a diaphragm flexing into the interior thereof. Lever means connect the tilt valve to the diaphragm so that as said diaphragm flexes internally it causes said lever to move and actuate the valve. A mouthpiece is connected to the interior of the chamber of the regulator for providing an inlet and outlet to a breather. The chamber at the mouthpiece interface is configured with a curved surface to enhance laminar flow and reduce turbulent flow into the chamber from the mouthpiece upon a user's exhalation. The curved surface limits backflow and stall, as well as limiting the separation of exhalation exhaust until proximate an exhaust valve. An exhaust valve opening within the chamber walls has an exhaust valve therein so that exhaust upon exhalation from a user can pass through said exhaust valve outwardly.