A sample cell (10) for a respired gas sensor has a single-piece injection molded main body (40) defining a gas flow path including an optical sampling bore (42) a gas inlet lumen (50) connected with the inlet end (44) of the optical sampling bore and a gas outlet lumen (52) connected with the outlet end (46) of the optical sampling bore. The gas flow path includes at least two curved walls (100 102 104 106). The sample cell may be manufactured by assembling mold pins (120 122 124 126 128) for defining the gas flow path wherein at least two mold pins (122 124) have curved surfaces for defining the at least two curved walls of the gas flow path and injection molding the single piece injection molded main body including removing the mold pins after defining the gas flow path including the at least two curved walls.
