Photoacoustic gas sensor comprising - a modulable infrared emitter, - a gas-fillable detection chamber, - a reference chamber, - a sensor channel connecting the detection chamber to the reference chamber, and - a sensor which is located in the sensor channel or is adjacent to the sensor channel, wherein the detection chamber is present in the beam path of the infrared emitter such that the infrared emitter can excite gas in the detection chamber by means of modulably emittable infrared radiation to generate a sound pressure and an equalization of the sound pressure through the sensor channel into the reference chamber can be detected in the sensor channel by means of the sensor, wherein the detection chamber, the sensor channel, the reference chamber and the sensor are arranged in a lateral plane which is substantially perpendicular to the radiation direction of the infrared emitter, wherein the detection chamber, the sensor channel, the reference chamber and the sensor element are formed in a multilayer substrate, wherein the reference chamber and the sensor channel with the sensor are not located in the beam path of the infrared emitter, the multilayer substrate is arranged substantially perpendicular to the radiation direction of the infrared emitter and formed by bonding at least two wafers and wherein a lower system wafer comprises the sensor and exhibits at least one lower cavity and an upper cap wafer comprises two upper cavities complementary to the at least one lower cavity such that the reference chamber and detection chamber are formed by bonding the lower system wafer and the upper cap wafer. - a modulable infrared emitter, - a gas-fillable detection chamber, - a reference chamber, - a sensor channel connecting the detection chamber to the reference chamber, and - a sensor which is located in the sensor channel or is adjacent to the sensor channel, wherein the detection chamber is present in the beam path of the infrared emitter such that the infrared emitter can excite gas in the detection chamber by means of modulably emittable infrared radiation to generate a sound pressure and an equalization of the sound pressure through the sensor channel into the reference chamber can be detected in the sensor channel by means of the sensor, wherein the detection chamber, the sensor channel, the reference chamber and the sensor are arranged in a lateral plane which is substantially perpendicular to the radiation direction of the infrared emitter, wherein the detection chamber, the sensor channel, the reference chamber and the sensor element are formed in a multilayer substrate, wherein the reference chamber and the sensor channel with the sensor are not located in the beam path of the infrared emitter, the multilayer substrate is arranged substantially perpendicular to the radiation direction of the infrared emitter and formed by bonding at least two wafers and wherein a lower system wafer comprises the sensor and exhibits at least one lower cavity and an upper cap wafer comprises two upper cavities complementary to the at least one lower cavity such that the reference chamber and detection chamber are formed by bonding the lower system wafer and the upper cap wafer. wherein the detection chamber is present in the beam path of the infrared emitter such that the infrared emitter can excite gas in the detection chamber by means of modulably emittable infrared radiation to generate a sound pressure and an equalization of the sound pressure through the sensor channel into the reference chamber can be detected in the sensor channel by means of the sensor, wherein the detection chamber, the sensor channel, the reference chamber and the sensor are arranged in a lateral plane which is substantially perpendicular to the radiation direction of the infrared emitter, wherein the detection chamber, the sensor channel, the reference chamber and the sensor element are formed in a multilayer substrate, wherein the reference chamber and the sensor channel with the sensor are not located in the beam path of the infrared emitter, the multilayer substrate is arranged substantially perpendicular to the radiation direction of the infrared emitter and formed by bonding at least two wafers and wherein a lower system wafer comprises the sensor and exhibits at least one lower cavity and an upper cap wafer comprises two upper cavities complementary to the at least one lower cavity such that the reference chamber and detection chamber are formed by bonding the lower system wafer and the upper cap wafer.