Boiler emits unusual smells (burning, plastic, or flue gas odour) during operation.

Safety first: If you smell gas or strong flue fumes, turn off the boiler and gas supply immediately, ventilate the area, and do not use the boiler until inspected. Burning plastic smells may indicate electrical overheating.

Step-by-step checks:

• 1. New or recently serviced boiler: Light burning smells can be normal for a short period as oils and dust burn off. This should diminish after a few hours of operation.
• 2. Visual inspection: With power off, remove the front panel and look for discoloured or melted wiring, connectors, or plastic parts. Do not touch components that appear damaged.
• 3. Check condensate trap and flue: Ensure the condensate trap is not blocked and that all flue joints are secure and correctly sealed.

When to stop: Any persistent or strong burning or flue gas smell requires immediate attention from a qualified technician. Do not continue to operate the boiler.