If microorganism are present in the test sample inoculated into the BACTEC vial,CO2 Will be produced when the organisms metabolize the substrates present in the vial. Increases in the fluorescence of the vial sensor caused by the higher amount of Co2 are monitored by the BACTEC fluorescent series instrument. Analysis of the rate and amount of CO2 increase enables the BACTEC fluorescent series instrument to determine if the vial is positive, i.e., that the test sample contains viable organism.