Gaseous smell from electric boiler room

We have an all electric house. No gas tanks. No gas BBQ.

We have wet under floor heating, we have an immersion heater.

We have all the tanks and electric boiler and expansion tanks etc in a “boiler room”

The boiler room has recently started smelling strongly of gas.

I am wondering if it’s a dead animal; but could there be any connection to the boiler etc?

Being summer, the only think in “operation” is the immersion hot water tank.