The quick release toggle vent valve (yellow) is fixed to the pannel of the Control Unit. It is used to rapidly flush the pressure after the B-reading. The handle must be in the horizontal  position when pressurizing the DMT and lifted in the vertical position to flush all the gas rapidly after the B-reading. When this valve is used to flush the gas, the C-reading may not be taken.

Important Note: The handle of this valve should normally be in the lifted position (flush) and lowered only during DMT readings. If the handle is rotated for more than 1 complete turn, it may damage and start leaking.