"Pete Cross" 1@2 wrote in message ...
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.