The IR-208 gas analyzer integrates two different types of gas measurement into one instrument. A multiple channel infrared detector array utilizing a single beam infrared optical system detects target gases using specially designed narrow band-pass optical filters. Comparing the infrared absorption of the reactive detectors to the nonreactive detector in the array provide the comparative for measuring the gas concentration in the sample stream. With a choice of more than 270 gases, up to 3 gases can be measured under infrared and up to 3 gases under electromechanical. The IR-208 also utilizes the chem-cell method to measure up to two more gases.