CO2 SensorsThere are currently two different methods of detecting CO2 gas, Nondispersive infared sensors (NDIR) and chemical sensors.
NDIR sensors measure the absorbtion of the characteristic wavelength of infared light as it passes through a light tube. As CO2 filters into the tube, the specific change in measured absorbtion signifies the presence of CO2. These sensors typically have sensitivities of 20-50 parts per million and usually cost between $100 and $1,000 in the (US). NIDR sensors are currently the most reliable method for detecting CO2
Chemical sensors utilize thin layers of polymer or heteropolysiloxane to detect CO2. Though smaller and size and power consumption, these sensors typically have a shorter life span than NDIR sensors.
A chemical sensor has been developed in the Netherlands that is based on hydrogel. Hydrogels are compounds that can shrink or swell in the presence of physical or chemical variables. One of these variables is pH. When CO2 enters the sensor, the pH change causes the hydrogel to swell, placing preassure on a preassure sensor.
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