Wood - Make sure you know what you're buying.

It is ESSENTIAL that the wood you burn on your open fire or in your wood burner / multi-fuel stove is properly seasoned (ideally for 2yrs) or kiln dried. Many of the sacks of logs you can pick up at garages, local shops or roadside vendors you will notice are quite weighty to lift - HIGH MOISTURE CONTENT! This is a false economy as it will not burn effectively and will coat the inside of your chimney or flue/liner with creosote (it is also dangerous as burning wet wood can produce high levels of Carbon Monoxide!). It is extremely acidic and if left to build up over time breaks down the mortar in your chimney, gradually destroying the chimney stack. It will also erode stainless steel greatly reducing the life of your liner/fluepipe. Creosote is  extremely difficult to remove and HIGHLY flammable - hence the large number of chimney fires in Cornwall! 

This is why if you are buying wood - buy wisely!!!!
(Please see below the link to a video explaining moisture content.)
 
Also be careful to avoid burning treated wood due to the harmful effects of the chemicals used. 
 
Remember to get your chimney/flue swept regularly and  your appliances checked and serviced by a CERTIFIED Chimney Sweep - http://guildofmasterchimneysweeps.co.uk/. 
 
Safety is key and nothing is more dangerous than fire!!!