Yes, Bosch has taken the decision to require CO detection with boiler interlock for any common cascade flue system where there is more than one boiler connected. With the increased popularity of cascaded boilers, we believe it is time to raise the bar on boiler room safety. CO detectors are now supplied as part of our cascade flue kits ready for on-site wiring, to make this transition simpler. For further information refer to the technical bulletin.