Wood-burning stove

Generally the appliance consists of a solid metal (usually cast iron or steel) closed firebox, often lined by fire brick, and one or more air controls (which can be manually or automatically operated depending upon the stove).

[4] This high number of deaths is due to the inhalation of toxic smoke emitted by improperly vented stoves, and contains substances harmful to health.

By opening or closing the dampers, air flow can be increased or decreased, which can fan the fire in the firebox, or "dampen" it by restricting airflow and reducing the flames.

Fully open air controls may lead to more heat being sent straight up the chimney rather than into the room (which reduces efficiency).

Overfiring is caused when too much heat is generated within the fire chamber, which will lead to warping, buckling and general damage to the stove and its internal components.

Hardwoods, derived from trees such as oak and ash, may burn at a slower rate, resulting in sustained output.

Hardwood tends to form and maintain a bed of hot coals, which release lower amounts of heat for a long time.

Moisture content can be reduced by outdoor air-drying ("seasoning"), for a period of several months in summer weather.

There are also stove models that can switch from wood fuel to oil or gas sources that are installed in the house to supply heat to a separate water boiler.

Modern wood stoves universally have some method of secondary combustion to burn unburned gasses for greatly improved efficiency and emissions.

This is why among modern stoves, catalytic models tend to be much better at achieving low, even heat output, which is desirable in warmer weather.

Modern non-catalytic wood stoves will also reburn the gasses from the firebox, but require a much higher temperature for the secondary combustion.

Stoves that do not employ any secondary combustion still exist, but are markedly less efficient and more polluting since unburnt products are left to leave via the flue.

In a conventional stove, when wood is added to a hot fire, a process of pyrolysis or destructive distillation begins.

The correct balance was difficult to achieve in practice, and many obsolete wood-burning stoves only admitted air above the fuel as a simplification.

Often the volatiles were not completely burned, resulting in energy loss, chimney tarring, and atmospheric pollution.

The technology is not actually new; it has been used for decades in industrial coal-fired boilers intended to burn coal with high volatile content.

Legal requirements for new installations in the UK can be found in Building Regulations Approved Document J, Section 2, Table 1 "Air Supply to solid fuel appliances".

[7] The safe operation of a wood-burning stove requires regular maintenance such as emptying ash pans (containers) beneath the wood grate.

The basic principle of controlling combustion by reducing the air supply means that very often there is a reduction zone/conditions within the stove.

In order to comply with the Clean Air Act in "smoke control areas", an exempt appliance or fuel must be used.

[8] The United States Clean Air Act requires that wood stoves be certified by the Environmental Protection Agency (EPA).

The New Source Performance Standards (NSPS) for Residential Wood Heaters, which came into effect on May 15, 2020.The EPA initiated wood stove emissions standards in 1988 to mitigate air pollution, setting the initial limits at 7.5 grams per hour for non-catalytic and 4.1 grams for catalytic stoves.

Previously, the EPA utilized crib wood, consistent in size and arrangement, for reliable testing burns.

However, this method didn't mirror actual stove usage in homes, where the more variable cord wood is standard.

This change aims for more realistic emissions testing, acknowledging the diversity in wood size, moisture, and type used in residences.

Nearly two million people are killed each year by indoor air pollution caused by open-fire cooking, mostly women and children, according to the World Health Organization (WHO).

[12] Non-governmental organizations (NGOs) such as Rotary International are actively assisting homeowners in constructing more fuel-efficient and safe wood-burning stoves.

[citation needed] It has been claimed that, in the UK, domestic wood burning has become the single biggest source of small particle air pollution.

(DEFRA) statistics do not support this claim [15] with road transport and industrial processes both being larger polluters.