Carbon Monoxide Leaks: One of the most serious concerns is the potential for carbon monoxide leaks. A damaged liner can allow combustion gases, including carbon monoxide, to escape into your home rather than being safely vented outside. Carbon monoxide is odorless and colorless, making it extremely dangerous as it can lead to carbon monoxide poisoning, which can be fatal.

Decreased Efficiency: A damaged liner can affect the efficiency of your furnace or water heater. The liner is designed to help direct combustion gases up and out of your home, and if it's damaged, these gases may not be efficiently vented, leading to decreased efficiency and higher energy bills.

Increased Fire Risk: If the damage to the liner is severe enough, it can increase the risk of a fire. A compromised liner may allow heat to escape and come into contact with combustible materials nearby, leading to a potential fire hazard.

Corrosion and Structural Damage: A damaged liner can also lead to corrosion and structural damage within the furnace or water heater itself. The liner helps protect the interior components from corrosive combustion byproducts, so if it's compromised, these components may be at risk of damage.

Moisture Issues: While some homes have switched to high efficiency furnaces, this change will lead to an incorrect sized liner for the water heater to vent. Too big of a space will not allow the gasses and moisture to escape quickly enough, forcing water to form and cause damage inside the home and deteriorate the chimney itself.