A flame sensor is a safety device that detects flames in heating systems to prevent gas leaks and explosions by shutting off fuel supply when no flame is detected. Key features include wavelength detection between 760 nm to 1100 nm, high sensitivity, and fast response time, with applications in fire detection systems and smart home automation. The document also outlines the types of flame sensors, their technical specifications, installation steps, and benefits of using Tomson Electronics' products.