It's responsible for transferring heat from the combustion chamber to the air that circulates through your home.
Check for cracks, rust, or holes. Examine the entire surface carefully.
Test for carbon monoxide leaks using a carbon monoxide detector. Shut down immediately if there are CO emissions.
For minor cracks, you can apply high-temperature furnace cement to seal them temporarily.
If it has significant damage, it’s best to replace it. Contact a licensed HVAC technician.