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 construction. These boilers are typically smaller and easier to maintain than water-tube boilers. They can be found in applications such as power plants, ship propulsion, and heating systems. Fire-tube boilers are known for their reliability and are often used in settings where space is limited.