Chimneys for liquid and gaseous fuels serve to discharge the flue gases from the combustion of gas or oil in heating appliances into the outside air. They not only must be temperature-resistant, but also must be resistant to flue gas condensate moisture and feature condensate drainage. Unlike Chimneys for solid fuels, chimneys for liquid and gaseous fuels do not need to be resistant to soot fire because they are not permitted to be used for the discharge of flue gases from the combustion of solid fuels.

Chimneys must be designed in such a way that no flue gases can escape into living areas and surrounding building components are not exposed to excessive temperatures. In cases where resistance-to-fire requirements exist in accordance with the Building Codes of the federal states (Landesbauordnungen), it must also be ensured that the fire cannot spread to other storeys.

Chimneys for liquid and gaseous fuels can be made of materials such as stainless steel, ceramics, concrete or plastic.

They can be designed as system chimneys or as custom-built chimneys.

System chimneys  are characterised by the fact that a single manufacturer is responsible for all of the different components included in the modular design. System chimneys can be designed with multiple walls, the term 'wall' referring to the flue liner carrying the flue gas, possibly an insulation product and/or an air/annular gap as well as the outer wall. Harmonised standards have been published for system chimneys.

Custom-built chimneys are assembled at the place of use from components that are either covered by harmonised technical specifications (harmonised standard or ETA) or for which national technical approvals (abZ) have been granted. These components can originate from different manufacturers and bear either the CE marking in accordance with the relevant harmonised technical specification or the German national conformity mark (Ü-Zeichen) in accordance with the relevant abZ.

Regulatory framework

In this work area, DIBt grants:

• national technical approvals (abZ) for chimneys for liquid or gaseous fuels and/or parts thereof that are not covered by an ETA or the applicable harmonised standards for chimneys (system chimneys) or for parts of chimneys (custom-built chimneys);
• general construction technique permits (aBG) for the execution of chimneys not covered by the execution standard DIN 18160-1.

National technical approvals and general construction technique permits can be granted together in a single decision ('combined decision').

European Technical Assessments (ETAs) can also be issued for chimneys or parts of chimneys that are not (fully) covered by a harmonised standard. For construction products covered by an ETA, a general construction technique permit for the application may be pertinent.

For dimensionally stable insulation products used in the execution of custom-built chimneys, voluntary verification (e.g. DIBt evaluations) is currently recommended if the application temperature limit for the insulation product lies above the flue gas temperature of the flue liners.

The technical rules to be observed in the execution of chimneys include:

• DIN EN 13384-1 – Chimneys – Thermal and fluid dynamic calculation methods – Part 1: Chimneys serving one heating combustion
• DIN EN 13384-2 – Chimneys – Thermal and fluid dynamic calculation methods – Part 2: Chimneys serving more than one heating appliance
• DIN V 18160-1 – Chimneys – Part 1: Design and performance

Please also note the relevant provisions of the federal states following MVV TB, Annex 8, Section 8.3 (2017/1) or Annex 14 (2019/1 and following).