What type of wood is this?

[fieldsportsman 107]

birch

[fieldsportsman 107]

or cherry

[toby63 1,236]

ash

[Born Hunter 17,910]

A liner is often considered necessary with a log burner (even when using a chimney from an pre existing open fire) because modern log burners are something like 90% efficient where as an open fire is something like 20% efficient. So, with an open fire % of the heat is in the smoke and so the smoke and gasses leave the chimney very quickly through convection. Obviously the efficiency of a modern burner means the smoke and gasses going up the chimney are a lot cooler and in such a relitively large space they can and do condense before leaving the chimney. This can cause a build of of shite in your chimney and build up of the deadly Carbon Monoxide in your house. A flue has reduced volume and so the smoke/gasses don't have chance to condense before leaving your chimney.