Fire-tube boilers are a type of steam boiler where hot gases from a fire pass through tubes that are surrounded by water. This design allows the heat from the gases to transfer to the water, producing steam. They are commonly used in various industries for heating and power generation due to their efficiency and relatively simple design. These boilers are typically smaller and easier to maintain than other types, such as water-tube boilers. Fire-tube boilers can be found in applications ranging from commercial heating to industrial processes, making them versatile and widely used in many settings.