Gas heater
Encyclopedia
A gas heater is a device used to heat a room or outdoor area by burning natural gas
or liquefied petroleum gas. Indoor household gas heaters can be broadly categorized in one of two ways: flue
d or non-flued, or vented and unvented. Gas heaters can be dangerous due both to risk of fire, and to the emissions, particularly in non-flued heaters.
invented in the previous year. It was first commercialized by the English company Pettit and Smith in 1856. The flame heats the air locally. This heated air then spreads by convection
, thus heating the whole room. Today the same principle applies with outdoor patio heater
s or "mushroom heaters" which act as giant Bunsen burners.
Beginning in 1881 the burner's flame was used to heat a structure made of asbestos
, a design patent
ed by Sigismund Leoni, a British
engineer
. Later, fire clay
replaced the asbestos because it is easier to mould. Modern gas heaters still work this way although using other refractory
material.
Modern gas heaters have been further developed to include units which utilize radiant heat
technology, rather than the principles of the Bunsen burner. This form of technology does not spread via convection, but rather, is absorbed by people and objects in its path. This form of heating is particularly useful for outdoor heating
, where it is uneconomical to attempt to heat a large volume of air.
, if properly installed with correct overall height, should extract most heater emissions. A correctly operating flued gas heater is usually safe.
. Non-flued heaters can be risky if appropriate safety procedures are not followed. There must be adequate ventilation – which is a problem due to the ventilation cooling the house, counteracting the heating – they must be kept clean, and they should always be switched off before sleeping. If operating correctly the main emissions of a non-flued gas heater are water vapour and carbon dioxide
. If there is incomplete combustion, toxic products such as carbon monoxide
and nitrogen dioxide
form. If ventilation is poor, the carbon dioxide
level in a room will begin to increase, and prevent the release of carbon dioxide
from the blood to the room air (see lung
) way before the decrease of available oxygen (or carbon monoxide
forming) becomes a problem.
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
or liquefied petroleum gas. Indoor household gas heaters can be broadly categorized in one of two ways: flue
Flue
A flue is a duct, pipe, or chimney for conveying exhaust gases from a fireplace, furnace, water heater, boiler, or generator to the outdoors. In the United States, they are also known as vents and for boilers as breeching for water heaters and modern furnaces...
d or non-flued, or vented and unvented. Gas heaters can be dangerous due both to risk of fire, and to the emissions, particularly in non-flued heaters.
History
The first gas heater made use of the same principles of the Bunsen burnerBunsen burner
A Bunsen burner, named after Robert Bunsen, is a common piece of laboratory equipment that produces a single open gas flame, which is used for heating, sterilization, and combustion.- Operation:...
invented in the previous year. It was first commercialized by the English company Pettit and Smith in 1856. The flame heats the air locally. This heated air then spreads by convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
, thus heating the whole room. Today the same principle applies with outdoor patio heater
Patio heater
A patio heater is an appliance for generating radiant heat for outdoor use.A burner on top of a post, burns LPG or propane, and directs the flames against a perforated metal screen. Heat is radiated from the surface of the screen in a circular pattern around the appliance...
s or "mushroom heaters" which act as giant Bunsen burners.
Beginning in 1881 the burner's flame was used to heat a structure made of asbestos
Asbestos
Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
, a design patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
ed by Sigismund Leoni, a British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
engineer
Engineer
An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...
. Later, fire clay
Fire clay
Fire clay is a term applied to a range of refractory clays used in the manufacture of ceramics, especially fire brick.High grade fire clays can withstand temperatures of 1775°C , but to be referred to as a "fire clay" the material must withstand a minimum temperature of 1515°C...
replaced the asbestos because it is easier to mould. Modern gas heaters still work this way although using other refractory
Refractory
A refractory material is one that retains its strength at high temperatures. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above...
material.
Modern gas heaters have been further developed to include units which utilize radiant heat
Radiant heating
Radiant heating is a technology for heating indoor and outdoor areas. Heating by radiant energy is observed everyday, the warmth of the sunshine being probably the most commonly observed example. Radiant heating as a technology is typically more narrowly defined...
technology, rather than the principles of the Bunsen burner. This form of technology does not spread via convection, but rather, is absorbed by people and objects in its path. This form of heating is particularly useful for outdoor heating
Outdoor heating
Outdoor heating allows people to stay in substantially unenclosed spaces, when it would otherwise be too cold to do so. To this end, various outdoor heating appliances are available, including gas patio heaters, quartz or ceramic electric lamps, and wood burning chimenea and fire pits.In an outdoor...
, where it is uneconomical to attempt to heat a large volume of air.
Flued heaters
Flued heaters would always be permanently installed. The flueFlue
A flue is a duct, pipe, or chimney for conveying exhaust gases from a fireplace, furnace, water heater, boiler, or generator to the outdoors. In the United States, they are also known as vents and for boilers as breeching for water heaters and modern furnaces...
, if properly installed with correct overall height, should extract most heater emissions. A correctly operating flued gas heater is usually safe.
Non-flued heaters
Non-flued heaters – also known as unvented heaters, ventfree heaters or flueless fires may be either permanently installed or portable, and generally incorporate a catalytic converterCatalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
. Non-flued heaters can be risky if appropriate safety procedures are not followed. There must be adequate ventilation – which is a problem due to the ventilation cooling the house, counteracting the heating – they must be kept clean, and they should always be switched off before sleeping. If operating correctly the main emissions of a non-flued gas heater are water vapour and carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
. If there is incomplete combustion, toxic products such as carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
and nitrogen dioxide
Nitrogen dioxide
Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...
form. If ventilation is poor, the carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
level in a room will begin to increase, and prevent the release of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
from the blood to the room air (see lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
) way before the decrease of available oxygen (or carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
forming) becomes a problem.