Just wondering how everyone is now classifying the ventilation on these boilers?. Suppose I have a j & s in a cupboard ventilated to the adjacent room, the vents are 50% undersized with no vent to outside. Combustion air is fed in via a vent in the loft into the return air duct and sized correctly with vents in the loft to outside all ok. Corgi say that all open flued appliances with compartment ventilation less than 90% is at risk. How do you guys classify this?