A flued boiler is a special type of machine that makes heat by burning things like coal, wood, or gas. Think of it like a big campfire inside a metal box. The fire heats up water that flows through pipes inside the box. The hot water then goes to where it's needed, like to make steam that can turn a machine or heat up a building.
The special thing about a flued boiler is the way it gets rid of the smoke and gas that comes from burning the fuel. Instead of just letting it go out into the air, there's a special pipe called the flue that takes it outside. So the boiler stays safe and the air stays clean.
But flued boilers can be dangerous if they're not used right. It's important to know how to control the flames and make sure the pipes are clear. Not just anyone can use a flued boiler without special training. So it's important to follow the rules and be careful with these powerful machines!