A system and method employing infrared laser spectrography and dual
wavelength modulation to monitor the concentration of a gas, such as
oxygen or carbon dioxide, in the sample vial, or to monitor the pressure
in the sample vial, to thus detect for microorganism growth in the sample
vial. The system and method each employ an energy emitting device, such
as an infrared laser, a detector and a signal analyzer, such as a
spectroscopy device. The infrared laser emits toward the container
infrared energy having a substantially single wavelength substantially
equal to a wavelength at which the gas absorbs the infrared energy. The
detector detects a portion of the energy signal that passes through the
container, and the signal analyzer spectroscopically analyzes the
detected portion of the energy signal to determine whether the gas exists
in the container, or to determine the pressure in the container. The
system and method thus determines whether an organism or cell of interest
is present or viable in the container based on the results of the gas or
pressure detection.