Fabrication of non-dispersive infrared sensor (NDIR) for detecting CO2 in indoor with low-level concentration towards human health safety applications

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Abstract

Carbon dioxide (CO₂) is known as a gas of global climate change and global warming as well as impacts on human health. Recently, scientific literature and documents have been shown that exposure at the CO₂ low-level concentration (~5000 ppm) for a long-time can affect human health and psychomotor performance. It is more serious in modern life when humans are usually in indoor environments with low ventilation rates such as school-rooms, office-rooms, buildings, etc. In indoor environments, the low-level CO₂ concentrations can be easy to obtain due to release from the processes like human metabolism, cooking, and fuel combustion. On the other hand, it is more dangerous because carbon dioxide is a colorless, odorless, and tasteless gas that is undetectable to the human senses and causes long-term and silent effects on human health. It can be related to respiratory, cardiovascular, kidney, bone, neurological, cognitive, and autism diseases, particularly in children and people with weak-physical conditions. In this work, the infrared absorption gas sensor was fabricated for detecting CO₂ in the range of low-level concentration (0 ¸ 10.000 ppm), towards applications in monitoring and conditioning CO₂ concentration in indoor environments. The configuration of the sensor is a non-dispersive infrared (NDIR) structure with two infrared detectors. A porous ceramic tube was used to gas self-diffusion from the environment into the gas-sampling chamber of the sensor. The NDIR sensor showed good performance with a resolution of 2 ppm, limitation of detection (LoD) of 0.5 ppm, and standard deviation of 10 ppm.