The paper "Metal Oxide Semiconductor Gas Sensors in Environmental Monitoring" by George F. Fine, Leon M. Cavanagh, Ayo Afonja, and Russell Binions reviews the use of metal oxide semiconductor (MOS) gas sensors in various environmental monitoring applications. These sensors are known for their low cost, robustness, lightweight, long lifespan, and high sensitivity to trace amounts of gases such as carbon monoxide (CO) and nitrogen dioxide (NO2). The review explores the fundamental principles behind gas sensing, including band theory and the interaction of gases with metal oxide surfaces. It discusses the synthetic routes to MOS sensors and their impact on surface structure, highlighting recent advances in sensor technology. The paper also addresses the challenges of sensor response disruption by non-target gases and the factors influencing sensor design. Techniques for sensor fabrication, such as screen printing, chemical vapor deposition (CVD), and physical vapor deposition (PVD), are compared in terms of advantages and disadvantages. The review then delves into specific applications of MOS sensors for detecting CO, NOx, NH3, and CO2, presenting recent advancements and future prospects. Finally, it describes innovative approaches developed at University College London, including the use of selective zeolite layers, new perovskite materials, and chemical vapor deposition for film deposition.The paper "Metal Oxide Semiconductor Gas Sensors in Environmental Monitoring" by George F. Fine, Leon M. Cavanagh, Ayo Afonja, and Russell Binions reviews the use of metal oxide semiconductor (MOS) gas sensors in various environmental monitoring applications. These sensors are known for their low cost, robustness, lightweight, long lifespan, and high sensitivity to trace amounts of gases such as carbon monoxide (CO) and nitrogen dioxide (NO2). The review explores the fundamental principles behind gas sensing, including band theory and the interaction of gases with metal oxide surfaces. It discusses the synthetic routes to MOS sensors and their impact on surface structure, highlighting recent advances in sensor technology. The paper also addresses the challenges of sensor response disruption by non-target gases and the factors influencing sensor design. Techniques for sensor fabrication, such as screen printing, chemical vapor deposition (CVD), and physical vapor deposition (PVD), are compared in terms of advantages and disadvantages. The review then delves into specific applications of MOS sensors for detecting CO, NOx, NH3, and CO2, presenting recent advancements and future prospects. Finally, it describes innovative approaches developed at University College London, including the use of selective zeolite layers, new perovskite materials, and chemical vapor deposition for film deposition.