It is 6yrs old, when the main burner is lit there is a small smell of gas from the modulating gas valve but I can't see any leaks after brushing detergent solution around anything that looks like a seal. There is a flat square plate on top with a visible gasket and a pipe comes off that up to the burners but other than that there doesn't look to be anywhere else it can escape. With the burner off and pilot lit there's no smell at all.
You may be confusing the smell of the product of combustion, which may be leaking into the room. Check the flue out.
The flue looks fine, it has two concentric tubes, the inner aluminium one carries burnt gas out and the outer plastic one sucks outside air in, it's fan assisted and the burner/fan/flue section is sealed from the room. Do gas valves leak eventually ?
Check out the case seal.
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