Gas sensor

A gas sensor comprising:

• a first light emitting part and a second light emitting part each emitting an infrared light;
• a first light receiving part and a second light receiving part each outputting an output signal in response to an incident infrared light;
• a first optical path region through which a light emitted from the first light emitting part passes until it enters the first light receiving part;
• and
• a second optical path region through which a light emitted from the second light emitting part passes until it enters the second light receiving part, wherein
• the first optical path region and the second optical path region have a common region in at least a part thereof;
• a rate of change of an output signal with respect to a change in concentration of a predetermined amount of first gas of the first light receiving part is larger than a rate of change of an output signal with respect to a change in concentration of the predetermined amount of first gas of the second light receiving part;
• a rate of change of an output signal with respect to a change in concentration of a predetermined amount of second gas of the second light receiving part is larger than a rate of change of an output signal with respect to a change in concentration of the predetermined amount of second gas of the first light receiving part;
• the first light receiving part has a first sensitivity peak wavelength;
• the second light receiving part has a second sensitivity peak wavelength;
• the first sensitivity peak wavelength is closer to a first wavelength in an absorption wavelength band of the first gas than the second sensitivity peak wavelength;
• and
• the second sensitivity peak wavelength is closer to a second wavelength in an absorption wavelength band of the second gas than the first sensitivity peak wavelength.