How can a single radiator heat all the air in an entire room?

A single radiator can heat all the air in a room through the process of convection. As the radiator warms up, it heats the air directly surrounding it, causing that air to rise and create a circulation pattern. This warm air displaces cooler air, which then moves towards the radiator to be heated, allowing the entire room to gradually warm up. Additionally, radiators can emit infrared radiation, which warms objects in the room, further contributing to the overall heating effect.