Gas Sensors - An Important Technology for Health, Home and Industry
Types of Gas Sensors
Semiconductor gas sensors: One of the most widely used type, these utilize metal-oxide semiconductors whose conductivity changes on reacting with gases. Taget gases include CO, NOx, H2S etc.
Electrochemical gas sensors: An electrochemical cell is used containing electrodes and an electrolyte. Gas diffusing through causes oxidation/reduction reactions leading to a change in voltage or current output. Popular for detecting O2, CO, H2 gases.
Infrared gas sensors: Detect specific gases using their unique infrared absorption signatures without coming in contact. Very accurate but more expensive than other types. Commonly used for toxic industrial gases.
Photoionization detectors: Uses ultraviolet lamp ionizing gas molecules. Presence of target gas alters output current which is calibrated to its concentration. Versatile detectors for volatile organic compounds.
Others include catalytic gas sensors, thermal conductivity sensors etc. depending on the target gases and application requirements.
Applications in Homes
Carbon monoxide (CO) gas sensors are mandatory in many countries for installation in homes due to the toxicity of CO. Even low concentrations over long periods can cause illness.Wall-mounted sensors sound an alarm on detecting CO, alerting occupants to ventilate the area immediately.
Natual gas detectors placed near Gas Sensor appliances and in basement warn of gas leaks from pipelines which could lead to explosions.Safety is ensured through automatic gas valve shut-off by the sensor in case of a high leak.
Indoor air quality monitors detect common pollutants like VOC's from paints, cleaning agents etc. and provide ventilation accordingly. This promotes a healthy indoor environment.
Smoke alarms use photoelectric sensors to detect smoke particles and warn during fires. Gas sensors in modern alarms distinguish real fires from other sources to prevent false alarms.
Importance in Industry and Automotive
Industrial gas detectors continuously monitor work areas for hazardous gases in factories and plants. Exposure alarms at set concentration thresholds ensure worker safety. Toxic gas leaks are immediately identified and contained.
Semiconductor fabs and cleanrooms use electronic nose systems with arrays of gas sensors for process monitoring and quality control. Detecting even parts-per-billion levels of impurities is critical.
Emission testing equipment at automobile production lines analyzes vehicle exhaust for regulated pollutants like CO, NOx, HC etc.using electrochemical sensors. This helps comply with stringent emission norms.
In-vehicle gas sensors provide feedback to emission control systems like three-way catalytic converters. Sensors upstream and downstream of the converter precisely regulate its operation.
Gas detection is essential in oil & gas facilities, landfill sites, wastewater plants and other hazardous locations. Wireless sensor networks monitor large areas remotely and continuously.
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