Many people restrict the air flow into their stove to slow the burn rate and save fuel. Unfortunately this runs the risk of forming creosote in the flue and thus chimney fires. Another result of burning at low temperatures is that it releases significantly more dust particles up the chimney and thus increases pollution. Looking at these two issues in more detail:
Creosote. The danger of burning at low temperatures is more pronounced with wood fires, as there is more moisture contained in even well dried firewood than other fuels (e.g. coal). A fire with a low burning temperature will result in lower temperature smoke, which cools further as it rises through the chimney. The low temperature means more unburnt particles in the smoke and these condense on the chimney walls forming creosote. This can damage the joints in the chimney and even seep through the walls. But the real danger with creosote is that it can catch fire and burn at a higher temperature,causing serious damage to the chimney and potentially your home.
Dust Particles. Burning at low temperatures produces much unburnt particles in the smoke and these escape into the atmosphere increasing dust pollution particularly in urban areas. A modern clean burning stove used correctly will produce between 2 and 4 grams of dust per kg of wood burned. By contrast poor burning technique and an out of date stove can produce dust emissions 20 times higher. The way we light the fire will also have an impact on dust generation and it should be noted that the previously discussed ‘upside down fire technique’ will produce a more complete burn and therefore less dust in the initial stages. See here. In Denmark regulations are expected that which will set a maximum dust emissions level of 5g/kg see http://eng.mst.dk/media/131065/statutory-order-on-wood-stoves-2015.pdf
As a result it is better for your chimney and the outside environment to maintain a good air supply into the stove so that the wood burns vigorously. It has the added benefit of keeping the glass clean. If this produces too much heat simply restrict the amount of fuel used and perhaps use softwood during warmer weather and leave the hardwood for the colder nights.