MOS-Based Gas Sensors for Monitoring of Air Pollution: A Review

Air pollution is one of the major concerns as it is the contamination of atmosphere air (indoor and outdoor) by harmful and toxic gases, chemicals, physical, or biological agents that alter the natural attributes of the atmosphere. Air pollution stems from both human activities and natural phenomena. Natural sources include volcanic ash, wildfire, smoke, colon, dust storms, forest fires, desert dust, sea spray, meteorites, volcanic eruption, redon decay, and fires. Human create another portion of air pollution, also known as man-made, or anthropogenic sources, which take the form of exhaust from planes, cars, aerosol cans, factory emissions, and even cigarette smoke, which is considered air pollution. The primary sources are automobiles and vehicles in the man-made category. Among the various sources, whether originating from human activities or nature, the primary toxic gases include carbon oxide, sulfur oxide, nitrogen oxides, and hydrocarbons. The substances pose significant risks to human health, agricultural activities, and environmental integrity. Hence, it is crucial to identify and regulate the emission of these harmful gases into the atmosphere. A gas sensor is crucial for managing and preserving a clean environment and ensuring the effectiveness of other safety technologies. This review thoroughly assesses gas sensors and crucial role in addressing the environmental pollution, explicitly focusing on air pollution. This review offers a comprehensive analysis of the semiconductor metal oxide sensors and their mechanisms and relevant factors affecting sensing. It discusses the historical context and fundamental concepts of gas sensors, emphasizing metal-oxide–semiconductor (MOS) gas sensor technology and its advantages over alternative sensor types. Additionally, it explores the performance parameters of MOS-based gas sensors and various methods to enhance their sensitivity and selectivity. The priority lies in crafting the article to benefit both newcomers seeking to delve into gas sensor research and established researchers, aiming to enhance the sensing capabilities of MOS, gas sensors.