A gas furnace is an enclosed structure that burns gas to produce heat for industrial purposes. They can be made with various kinds of heat resistant (refractory) elements to withstand long-term use. The enclosed space holds the gas being heated until the desired temperature is reached within the furnace.
Rising electricity prices make gas-fired furnaces an economical choice for heating applications, while also reducing harm to the environment. Most new gas furnaces tend to be grouped in one of two general classes of efficiency: power combustion at 80-82% AFUE and condensing furnaces that are at least 90% efficient. Condensing furnaces are used in most situations, with the exception of warm climates. Condensing furnaces are much more resistant to corrosion caused by condensation in the unit or a chimney. These models typically exhaust through a plastic pipe that exits through a side wall, and do not need to use the chimney, which was typically the case with combustion furnaces. As most models are now gas-fired, very few oil-fired condensing furnaces are available.Gas furnaces can come with varying temperature control options or be set for a single temperature, depending on the process for which the furnace will be used. Gas furnaces commonly have one of the following atmospheres: air or oxidizing, inert, reducing, salt bath or vacuum. Over-temperature protection, service or entry holes, three-zone or multi-zone, view ports, computer interface and application software are some of the options available for these furnaces. Gas furnaces use natural gas as a source of heat. When considering whether to replace an existing gas furnace, the decision depends on the furnace's age, condition and current performance. The steel industry is one of the many industries that use high-temperature, natural gas-fired furnaces, which produce large amounts of nitrous oxide (NOx) per unit of processed material. To meet increasingly stringent emissions regulations, oscillating combustion technology has been developed and is continuing to be improved for use with gas furnaces. This technology provides efficiency, productivity and reduced nitrous oxide emission from all types of industrial furnaces. A typical heating system will last about 25 years, though some gas furnaces can last twice that long.