Photoacoustic spectroscopy（PAS）is a very attractive technique for gas detection.Nonresonant photoacoustic gas detection system shows good expectation because of the simple structure and low cost.A gas detection system based on a MEMS infrared emitter

an electret microphone and a nonresonant optoacoustic detector with single and double chamber has been built and the gas sensing properties for different volume fraction CO2 have been tested with the optimum frequency of the infrared source emitter.The nonresonant optoacoustic detector with double chambers shows higher signal intensity and lower detection limit than the detector with conventional single chamber.The detection limit of the single chamber detector system is about 7.2×10-6

and the double chamber detector system is about 2.1×10-6.