Smoke detectors are mandatory in residential property in all 16 German states – but the details, especially maintenance responsibility, differ state by state.
Which rooms need detectors
The common core across all state building codes: bedrooms, children's rooms and any hallway serving as an escape route. Berlin and Brandenburg go further and require detectors in all habitable rooms.
Installation: the owner's job
Installation is the owner's/landlord's duty nationwide. Purchase costs cannot be passed on through service charges, and courts have grown sceptical of rental-device schemes.
Maintenance: a state-by-state patchwork
In most states, keeping detectors operational falls on the occupant – the tenant – unless the owner has assumed maintenance. Leases and owners' association resolutions should assign this explicitly; where the landlord maintains the devices, the running costs are recoverable as "other operating costs" if agreed in the lease.
Liability
A missing or non-functional mandatory detector creates serious civil and criminal exposure, and building insurers do check compliance after a fire. A documented maintenance record per flat is invaluable; in eigentumwerk it can be stored per unit and scheduled as a recurring task in the ticket system.