The efficient control of woodburning and multifuel stoves is achieved by using the air controls. The operation of the different air controls fitted to modern stoves is explained below:-

- PRIMARY AIR CONTROL

This is the lower air control and it provides either the initial lighting air supply on a Woodburning stove or the main combustion air on a Multifuel stove.

- AIRWASH (SECONDARY) AIR CONTROL

This is the main air control on a Woodburning stove and regulates the stoves output.  On Multifuel stoves the secondary air is normally left at 50% once lit, with stove output regulated by the primary air control.

- CLEANBURN (TERTIARY) AIR CONTROL

This third air control (where fitted) normally injects air at the rear of the stove through a row of small holes.  Without cleanburn air, stoves can run out of oxygen when volatile components of the wood are being burnt (wood gases). When this occurs we see brown smoke being generated. The cleanburn air supply is normally factory preset and provides an afterburner effect to ensure that the wood gases are thoroughly burnt in the fire-chamber.  Cleanburn minimises tar condensation in the stove or flue and reduces smoke emission.  Cleanburn also raises combustion efficiency and reduces ash.    

The two basic types of stove (and inset fire) are woodburning and multi-fuel. The main differences are described below;

WOODBURNING STOVES
These usually do not have a raised grate, the wood burns directly on the base of the stove. This is because wood burns best on a bed of ash with (secondary) air from above. Fossil fuel must not be burnt on a wood-burning stove.

Smokeless Zone Restrictions
Under the Clean Air Act regulations wood fuel may be burned in a 'Smoke Controlled Area' using an"Exempt" appliance. Stovax and other manufactures now offer stoves meeting these regulations. Visit solidfuel.co.uk for the "Exempt" stove list.

MULTI-FUEL STOVES
These have a raised grate -static or riddling- plus an ashpan. This is because fossil fuel needs an air supply through the firebed (grate) to maintain combustion. Wood can be burnt on a multi-fuel stove, however not all multi-fuel stoves incorperate the cleanburn air system for the efficient combustion of wood.