There are several different types of flues that can be used with gas boilers

A flue is a pipe or chimney that is used to vent gases from a gas-fired boiler to the outside of a building. The flue serves two main purposes:

To vent harmful gases, such as carbon monoxide, to the outside of the building, where they will not pose a danger to the occupants.

To allow the boiler to operate efficiently by allowing the gases to be vented out of the building.

There are several different types of flues that can be used with gas boilers, including:

Metal flues: These are typically made of stainless steel or aluminum and are used with most types of gas boilers. They can be either ventilated or non-ventilated, depending on the type of boiler and the local building codes.

Plastic flues: These are made of a durable plastic material and are typically used with newer, high-efficiency boilers. They are lightweight and easy to install, but they can be more prone to condensation than metal flues.

Balanced flues: These flues are typically used with sealed-combustion boilers, which do not require a chimney. They consist of a pipe that is vented to the outside of the building, with a separate intake pipe that brings in outside air for combustion.

It is important to choose the correct flue for your gas boiler to ensure that it operates safely and efficiently. A qualified heating technician should be able to help you choose the right flue for your specific needs.