Gas sensing device

A gas sensing device adapted for detecting a concentration value of a to-be-detected substance in an respiratory gas that is exhaled by a user, under exposure of light, the to-be-detected substance absorbing a portion of the light having a first absorption wavelength and a second absorption wavelength different from the first absorption wavelength, said gas sensing device comprising:

• a housing that has a respiratory gas inlet adapted for entrance of the respiratory gas into said housing;
• and
• a sensing module that is disposed in said housing, and that includes
• a light chamber adapted to permit the respiratory gas to pass therethrough,
• a light source unit configured to emit the light into said light chamber,
• a first light sensing unit including
• a first light filter that is disposed downstream of said light chamber, and that is configured to permit passage of a first portion of the light which has passed through said light chamber and whose wavelengths fall within a first wavelength range, the first absorption wavelength falling within the first wavelength range;
• and
• a first sensor that is disposed downstream of said first light filter, and that is configured to receive the first portion of the light which has passed through said first light filter and to output in real time a first detected signal indicating a first detected intensity of the first portion of the light,
• a second light sensing unit including
• a second light filter that is disposed downstream of said light chamber, and that is configured to permit passage of a second portion of the light which has passed through said light chamber and whose wavelengths fall within a second wavelength range different from the first wavelength range, the second absorption wavelength falling within the second wavelength range, and
• a second sensor that is disposed downstream of said second light filter, and that is configured to receive the second portion of the light which has passed through said second light filter and to output in real time a second detected signal indicating a second detected intensity of the second portion of the light, and
• a processing unit electrically connected to said first sensor and said second sensor, and configured to determine, based on the first detected signal and the second detected signal received therefrom, that the to-be-detected substance exists in the respiratory gas when a difference occurs in each of the first detected intensity and the second detected intensity over time.