A build up of soot and/or tar, infrequent sweeping, burning unseasoned timber or slumbering your stove (particularly trying to keep it going overnight) can lead to a chimney fire within the flexible liner of your stove. The picture above shows the typical evidence of at least one chimney fire in a liner.
Sometimes you can hear the chimney fire roaring, sometimes you can see flames coming out of the top of the chimney, sometimes the walls of a flue get very hot and sometimes you wont know until your sweep visits.
A fire in your liner can be serious and melt or deform the liner rendering it useless. The only way to establish the impact of a fire on a liner is to examine it with a CCTV camera. We have discovered melted structures, collapsed liners, unravelled liners and a host of other issues, all as a result of fires within flues.