Gas Boilers Is It Legal For A Block Of Apartments O Have A Shared Exhaust Duct Coming From Their Gas Boilers?

Is it legal for a block of apartments o have a shared exhaust duct coming from their gas boilers? - gas boilers

My carbon monoxide detector is triggered when someone in another apartment of your gas heater is. An engineer told us today that the flu will not close and if we feedback from other apartments. I live in Ireland.
It is a matter of life or death, no guesses please. What can I do?