Your boiler’s burner gasket — also known as the burner seal — is a vital safety component. It creates an airtight seal between the burner and the heat exchanger, ensuring that harmful flue gases remain fully contained and do not escape into the boiler casing.
The gasket ensures correct combustion and prevents carbon monoxide (CO) from entering the boiler casing. Over time, heat and pressure can cause the gasket to harden, crack, or lose shape — which can compromise its ability to seal properly.
Yes — in Worcester Bosch boilers, the terms “seal” and “gasket” refer to the same type of component.
Worcester tends to use the word seal, especially for:
But technically, these are all gaskets, because they serve the same function: creating an airtight, watertight, and combustion-tight seal between two surfaces. So:
During an annual boiler service, the burner gasket is inspected visually and tested using a flue gas analyser to confirm safe combustion.
Two tests can help identify gasket failure:
A flue gas analyser is used to check for any carbon monoxide (CO) readings around the burner. A normal reading means combustion gases are contained — but this alone doesn’t always confirm gasket integrity.
A controlled smoke match is lit near the burner to assess airflow. If the burner draws in the smoke, it indicates that air is being pulled through the failed gasket instead of the sealed air path.
This confirms that the gasket’s integrity has been lost and replacement is required immediately.
A degraded or damaged burner gasket can lead to:
Even a small breach can alter combustion ratios and cause instability, so this is not something to ignore.
If your boiler is over five years old, the burner gasket should be checked and replaced if there are any signs of wear, corrosion, or air leakage. Always ensure that the replacement is a genuine manufacturer part fitted by a Gas Safe Registered engineer.
Cost estimate:
Labour: £150
Parts: £10-20 (depending on boiler model)
20th August, 2026
18th March, 2026
