We have flues to gas boilers in the common area riser cupboards in our block of flats. The flues lead to the boilers within the flats. Do we need to install carbon monoxide detectors in the common areas where the cupboards are located? Thanks.

The law only requires that a carbon monoxide detector be installed in any room with any fixed-combustion appliance (excluding gas cookers) in privately rented homes and social housing, it doesn't mention the flue run. 

You can read the government document if you  Click here