If there is doubt about the condition of a chimney, or an old chimney is to be put in use after a long period of disuse, it is advisable to have it smoke tested.
Purpose
It must be remembered that the purpose of the smoke test is to identify any faults which would cause fumes to escape during the normal operation of the appliance and chimney.
Protection
A clay, concrete, or stainless-steel flue system is designed to protect the chimney walls from heat and corrosion. Where flue gases are allowed to penetrate to the chimney bricks and mortar the result would be a significant reduction in the usable life of the chimney. Due to the acidic nature of what is being burnt, your chimney will start to erode which can cause heat to transfer to combustible materials which were once considered safe (joists) and carbon monoxide can leak into your living space.
Regulations
According to building regulations it is possible to connect to a clay or concrete flue system that is fit for purpose, however many manufacturers recommend connecting to a flue which is equal to or only slightly larger than the outlet of the stove to maintain the efficient operation of the wood burner, incorrectly sized flues can lead to an excessive build-up of tar/creosote which is highly flammable and can lead to a chimney fire.
Lining
Clay liners are inexpensive, readily available, and perform quite well for open fireplace chimneys that are properly maintained. However, when considering the flue temperature associated with the running of a wood burning stove, clay liners cannot rapidly absorb and evenly distribute heat during the rapid temperature rise that occurs during operation, causing the clay flue lining to crack and split apart. As is the case with a brick and mortar chimney, the clay lining will deteriorate over time.
For those who are looking to build a new chimney, we would recommend installing a pumice flue system.
