Why do you need a chimney liner?

You may ask, “Why do you need a chimney liner?”.  You may think that your chimney has been there for almost a hundred years and as far as you know it is safe.  So why is my chimney sweep telling me I need to install a chimney liner now?

Chimney liners are designed to keep the harmful gases of your furnace or creosote from the stove inside the chimney and keep them from entering your home. Many homes have a chimney with very old technology. They have terra cotta (clay) flue liners. They were designed to work with coal, they still do work for coal. But now very few people burn coal as a main heating source.

Why do you need a chimney liner if you are burning gas, oil or wood?

Today many people burn natural gas and home heating oil. The terra cotta flues were not designed to withstand the acids inside the exhaust. Wood burning stoves create creosote, that when hot, is a flammable liquid. This creosote can be seen in the picture leaking into the home.  This is an extremely dangerous chimney.  As you can see the flammable creosote is now entering into the home and can easily ignite, catching the home on fire.  With gas and oil burning appliances, eventually the terra cotta deteriorates, creating he possibility of the chimney flues falling over inside the chimney.  This will creat a blocked chimney, a very dangerous situation for your family.

You need a stainless steel chimney liner, it is what will stand up to the harsh exhaust from a modern furnace and the dangerous creosote from a wood stove.

Why you need a chimney liner?
https://www.chimneylinerdepot.com/articles-2/chimney-liner-articles/do-i-need-a-chimney-flue-liner/