Complaints about a central boiler should be directed to a building's superintendent, landlord or the boiler manufacturer. If a boiler is not working correctly it is imperative to report it promptly for safety reasons.
Boilers should be maintained by the person or company that is in charge of the building it is in. Sometimes this can be a land management or realty company instead of the actual owner of the building. Any building manager should be able to direct complaints to the appropriate party so that repairs can be completed as soon as possible.
If a malfunctioning boiler is emitting gas fumes or otherwise appears to be creating immediate danger, it is best to call 911.