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Modern open fireplace

A chimney (from the Latin caminus ' oven ' ; in Switzerland and French-speaking countries, chimney ) is a technical facility for burning solid fuels  - mostly lumpy firewood , including peat  - that burn at a controlled speed.

The aim is primarily the heating of the installation and the comfort of the heat radiation of the open fire. With the spread of other room heating options, the decorative effect of the play of flames came more to the fore.


Fireplaces are usually (even from a combustion chamber, a flue collector Esse called) and a connecting line to a chimney . Additional components can be: a grate, thermal insulation to protect adjacent building fabric, a smoke flap and doors to close the combustion chamber.

The firebox is made of a non-combustible material, preferably it is lined with refractory bricks. Alternatively, the combustion chamber can be made from cast iron plates. Fireboxes industrially produced from sheet steel requires an additional lining (z. B. chamotte , vermiculite , calcium silicate ) in order to protect the steel sheet from direct flame attack. The smoke collector and the connecting pipe are also made of a non-flammable material; sheet steel is preferred today.

The technical components of the fireplace are clad or bricked up towards the room. Often the fireplace is placed in front of a back wall and protrudes into the room. The chimney is located behind, above or next to the chimney to remove the flue gases.

Difference between fireplace and stove

The nomenclature is not clear. A chimney is usually a structure and therefore belongs to the building. Today, a distinction is made between open chimneys and chimneys that can be operated closed (heating chimney). In some cases, a fireplace can also be operated openly. Ovens are mainly operated with a closed firebox, so they always have a door or flap and are often free in the room. An oven can also be a structure and thus belong to the building (tiled stove, pizza oven). Ultimately, the focus of a stove is always on the heat output.

Special case wood stove

Fireplace stove in operation

The term stove was generated in the 1970s and is based on the clearly visible play of flames behind a glazed door or flap. The stove enables good heat gains while at the same time atmospheric gain due to the clear visibility of the fire. With classic tiled or workshop stoves, there is usually no or almost no view of the fire, because the focus there is on the heat emission.

History of the fireplace

Open fireplace from the Grand Théâtre de Genève from 1879
Ornate detail of an open fireplace (around 1800), Carrara marble , bronze

Open fireplaces are classic fireplaces. They have been detectable for around 800 years. The historical predecessor of the chimney is the open house fireplace, which can be found up to the early modern era , where the smoke gases were openly led into the room. Later, free-hanging "smoke chimneys" made of clay pegs were used to discharge the smoke gases in a more controlled manner towards the roof ridge . With the spread of the multi-storey building method, the open house fire turned out to be impractical and was initially relocated from the center of the room into or against the outer walls. The smoke gases were led into a smoke collector located above the fireplace and led outside through slits in the walls. In rural areas, local fire protection regulations often only required the construction of brick chimneys that ran over the roof from around 1850 .

The open chimneys were initially used - with the exception of representative or stately buildings, parts of buildings or rooms - as a domestic hotplate and room heating. If historical chimneys were intended exclusively for space heating, they often feature elaborate cladding, natural stone applications and front style frames as an expression of a sophisticated lifestyle.

The following are differentiated: Lombard chimneys with a protruding, pyramid-shaped casing that stands on consoles or other protrusions; French who stand completely outside the wall; Germans, who protrude even further and have a high coat, and Dutch, who lie entirely in the wall.

Orders from Count Palatine Karl IV. From 1772 also served to prevent a fire in connection with domestic fireplaces. According to the simultaneous building regulations, no more wooden chimneys were allowed to be erected, no more wooden hoses were allowed to be installed, which had to lead the smoke from the fireplace to the fireplace, just as it was forbidden to lead stovepipes out of the window.

Fireplaces classified according to different criteria

Fireplaces can be grouped according to their characteristics. The common criteria are closed / open furnace, type of fuel and use.

Open and closed

Open fireplaces have a combustion chamber that is open to the room. A large percentage of the heating effect is lost in this construction through the chimney. Due to the low temperature of the combustion chamber and the impossibility of metered addition of air, emissions from open fireplaces are higher than from closed combustion chambers.

In terms of fire protection, when constructing open chimneys, care must be taken to ensure adequate and non-combustible thermal insulation, the use of suitable materials, installation on non-combustible and stable subsoil and a non-combustible floor covering in front of the combustion chamber opening. The floor covering should protect against sparks jumping out. The closed chimney (in the modern variant called a heating chimney) consists mostly of sheet steel or cast components. In contrast to the open fireplace, the closed one is closed with a usually glazed door in front of the combustion chamber or the combustion chamber towards the installation room. This can be made of iron (cast iron) or steel. The secondary air volume flow required with open chimneys is omitted , so the room air can be heated better.


Different types of fuel can be used in a fireplace depending on its design.


The first materials were made of wood. Even today, wood, so-called split logs , is very popular for burning. These types of wood include birch , beech , oak and alder , among others . Beech has the advantage of producing a pleasant scent for many when burned. With coniferous wood, care must be taken to ensure that there are low flying sparks and low resin flow. Wood briquettes are also suitable for burning in the fireplace . Pellets are not intended for general fireplaces and stoves. So-called pellet stoves were manufactured for the use of pellets as fuel.


Mainly hard coal and lignite are used. Hard coal has the greater thermal efficiency, but lignite is much cheaper.

Alternative fuel

Other fuels are possible depending on the type of fireplace. So peat is used, which when dried can generate almost as much heat as lignite. The 1st Federal Immission Control Ordinance (BImSchV), ordinance on small and medium-sized combustion systems, specifies exactly what can be burned in which ovens . According to this, for example, painted and varnished wood can be burned if it has not been treated with wood preservatives. Recycled paper or the pressed version of paper briquettes, on the other hand, do not belong in a fireplace. The stoves are not designed for this type of fuel and could produce high levels of emissions or contaminate the fireplace. A catalog of fines was drawn up to ensure compliance with the BImSchV.

Use and mode of action

Most wood-burning stoves work with radiant and convection heat . In addition, there is also use for hot water preparation or with electricity.

The heating effect of the open fireplace is based on the one hand on the heat radiation emitted directly from the flames . On the other hand, the usually solidly manufactured combustion chamber is heated in the course of the burn-up and thus provides additional radiant heat.

In historical constructions, the back of the combustion chamber sometimes borders on neighboring rooms, so that heat can also be given off there by radiation and convection.

The efficiency of open chimneys is low. The reason for this is that with the correct system design (depending on the internal dimensions and height of the chimney as well as the opening area of ​​the chimney), the opening of the chimney must be subjected to a considerable secondary air volume flow. On the one hand, this prevents flue gases from flowing out of the open combustion chamber to the installation room.

Description of the combustion air

On the other hand, this means that any heated room air is led out of the room via the chimney.

A functional requirement for open fireplaces is that sufficient combustion air and secondary air can flow into the installation room. As a rough estimate, an air requirement of 360 m³ / h per m² combustion chamber opening can be assumed.

Special constructions also lead room air behind the combustion chamber or through the smoke collector ( Esse ) and thus also enable heat to be dissipated by convection .

Radiant heat and convection heat

The radiant heat is given off through the firebox until it hits objects that absorb the heat. This includes the human body. Convection heat is dissipated through the air exchange through the chimney. In contrast to the radiant heat, this heat is given off into the environment via the outside of the stove. The heat is created by convection. Since warm air is lighter than cold air, it is blown through the chimney. Most of the pollutants caused by the burning process (emissions, fine dust) go with it. By withdrawing the warm air, negative pressure is created, which directs new air into the chimney. This can be introduced through the chimney or through the standardized supply pipes for combustion air, which are attached horizontally through the wall to the chimney. With the new air comes new oxygen, which is essential for the further burning process. Furthermore, there may be an additional supply for a so-called windshield washing air. This has the function of protecting the combustion chamber disc from sooting. Sooting is caused by too high or too low a negative pressure in the chimney.

Electric heat

Electric heat is the conversion of electrical energy into thermal energy in a heating resistor . Heat is generated by flowing electricity through a conductive metal with a low resistivity .

Hot water production

In the closed chimney used for central heating, the air ducts for fresh air and flue gas are optimized. The double-walled side walls, the fire grate and smoke gas pockets in the firebox are water-cooled. The water acts as an energy carrier. The heated water is fed into living rooms via the heating network or is used to supply hot water. The water-bearing chimney (technical name: chimney boiler) is used as an independent heating system or to relieve other heating systems as secondary heating. According to technical classification, the water-bearing fireplace is a solid fuel boiler, but with the design of a traditional fireplace. Four water pipes lead to a chimney boiler: two pipes to and from the hot water tank with its own water pump, one pipe for emergency cooling (if the pump fails) from the fresh water network and one pipe for discharging the emergency cooling water into the sewer system.

Decoration / wellness

In addition to its heating function, the fireplace has always had a decorative function. These use novel fireplaces such as gel fireplaces and bio-ethanol fireplaces. A fire flickers in them, which is not intended to generate heat, but only to relax. About 34 percent of fireplace owners own the device for reasons of romance. Wellness is the second most important reason to buy a fireplace or stove.

Types of chimneys

Fireplaces can be classified according to their functions and fuel. The following chimneys and stoves can be defined.

Gel fireplace

Gel chimneys are also available on the market without a chimney flue, an exhaust air option is not necessary. The fuel is ethanol (ethyl alcohol), which is mixed with special thickeners so that a paste-like liquid is created ( fuel gel ). This gel is poured into the designated burning cans and then ignited. A gel fireplace has a very low heat effect and is used for decorative purposes only.

Bioethanol fireplace

Bioethanol stove

Like gel fireplaces, bioethanol fireplaces also use bioethanol as fuel. Since no thickeners are used, the alcohol remains liquid and is poured into the intended combustion chamber. Bio-ethanol is used so that the fuel can burn without residue. A bioethanol fireplace has a decorative function. A chimney of this type hardly produces any heat, and an exhaust pipe is not required. Bioethanol fireplaces can be called alcohol fireplaces.

The Stiftung Warentest points out that ethanol fireplaces can be dangerous because the flame can come out of the device, especially while it is being refilled. The flame can spread easily (" deflagration ") and serious injuries are possible. That is why you should never refill a fireplace that is still warm.

Furthermore, the regulations of DIN standard 4734 for checking ethanol fireplaces should be observed.

Emergency chimney / additional chimney

An “emergency chimney” is a very simply constructed chimney that is used for temporary heating using solid fuels in times when there is no gas or oil supply (emergency). An “emergency chimney” was at times a building law requirement for new houses in Austria .

Tiled fireplace

The tiled fireplace combines the properties of a fireplace and a tiled stove. As is typical with a wood-burning stove, the combustion chamber is shielded by a transparent pane, the fire in the fireplace is visible. In addition, the cladding consists of heat-storing stove tiles . The heat is emitted into the environment as radiant heat and is also stored in the stove tiles. This means that residual heat remains even after the fire has gone out.

Pellet stove / pellet heating

The pellet stove, also called pellet fireplace or pellet stove, uses pellets to generate heat. Pellets are tiny particles of wood produced under pressure. The process is already known from the animal feed industry. According to the manufacturer's instructions, the pellets are filled into a storage container and automatically or manually poured into the combustion chamber. Since the pellets have a uniform density, the heat and fire usually remain uniform. The heat is radiated into the environment through a circulating air grille. The ignition takes place automatically (electronically) via an ignition wire.

Gas fireplace

In new buildings in the United States, to save space inside, the gas fireplace is sometimes housed in a box that protrudes from the wall.

Gas fireplaces are operated with natural gas or liquid gas . Gas is fed through a burner bed into the combustion chamber and burned there. These fireplaces are often controlled using a remote control . The ignition takes place via a piezo element and a starting flame with temperature monitoring. The advantages of gas fireplaces are the increased comfort (no manual fuel loading, no ash disposal or cleaning) with at the same time deceptively real wood fire imitation.

Here, too, a distinction is made between open and closed systems towards the room. Today, closed systems are mostly operated independently of the ambient air. Exhaust gas disposal and supply air take place via a concentric double pipe, the inner pipe forwards the exhaust gases and the supply air is supplied to the combustion chamber in the annular gap between the inner and outer pipe. The yellow color of the flame during combustion (gas burns stoichiometrically with a blue flame) results in closed systems from a slight lack of oxygen. The initially incomplete combustion directly above the burner bed creates soot particles, which then emit yellow over the length of the flame. Imitation wood, but also gray or white pebbles are usually used as burner bed supports. In closed systems, the regulation can be controlled by room temperature, that is, if the temperature falls below a specified minimum, the gas flame rises automatically.

Electric fireplace

The electric fireplace consists of an electric heater with a decorative fire. The fire is simulated using an installation kit. A connection requirement is a socket for the low-voltage network , in Europe 230 V, 50 Hz.

Fireplace cassette

A fireplace cassette is a closed, complete combustion chamber (without a smoke collector) that is subsequently inserted into an open fireplace and operated there. The cassettes are usually rear-ventilated: room air enters in the lower front area, is heated behind the cassette and released back into the room in the upper front area. The purpose of retrofitting cassettes is to increase the heat output to the room while at the same time increasing safety due to the combustion chamber being closed to the room.

Fireplace insert

A fireplace insert is the technical component of an industrially prefabricated and complete heating fireplace. The fireplace insert requires a handcrafted or industrially prefabricated cladding. Water-bearing fireplace inserts are also available. The water heated in the water pocket can then be used to heat radiators installed in other rooms . In addition to the heating circuit , a water inlet and a water outlet are usually required in order to be able to cool the insert in the event of overheating.

See also

Web links

Wiktionary: Fireplace  - explanations of meanings, word origins, synonyms, translations
Commons : Fireplace  album with pictures, videos and audio files

Individual evidence

  1. ↑ Advisor for the half- timbered house - Section “D.1 Chimney / Chimney”. (PDF), page 108. Umburbehaus Foundation, accessed on May 20, 2020 .
  2. ^ Franz-Josef Sehr : The fire extinguishing system in Obertiefenbach from earlier times . In: Yearbook for the Limburg-Weilburg district 1994 . The district committee of the Limburg-Weilburg district, Limburg-Weilburg 1993, p. 151-153 .
  3. ^ Fuel heating value , BUND NRW eV, accessed May 15, 2015
  4. ↑ Heating systems and heat dissipation. In: . Retrieved June 5, 2020.
  5. Ethanol fireplaces - the underestimated danger . In: Research compact . No. 09/2014 . Fraunhofer-Gesellschaft , September 2014, ISSN  0948-8375 ( [PDF; 456 kB ; accessed on May 17, 2020]).
  6. Ethanol fireplace - a fire-hazardous decoration. In: . January 23, 2020, accessed April 27, 2020.
  7. warns of ethanol fireplaces - danger in the living room. In: . December 1, 2010, accessed November 11, 2019 .