So the question is......."How can I know if my chimney liner is ok?" Sometimes it is easy! Please see above photo of a crumbling chimney liner that has seen better days! Other ways of knowing are to check the top area of the exposed liner. Do you see cracks or deterioration? If you're not sure you can always have a qualified chimney sweep clean and inspect the liner for cracks. A cracked chimney liner is a potential fire hazard.
Any questions? Please email or call me anytime. That's all for now! Ed