Fire safety duties under the Regulatory Reform (Fire Safety) Order 2005 fall on the "responsible person". Who that is depends on one thing: who has control of the premises, or of the part of them you are asking about.
Control, not ownership, decides
You can be responsible for a building you do not own. Anyone who has control of premises to any extent takes on the duties for the matters within their control. That includes a person who has an obligation under a contract or tenancy to maintain or repair the premises, or to keep them safe, to the extent of that obligation.
Your lease, tenancy agreement and any management contract show who has those obligations for each part of a building.
Who is responsible in common arrangements
A building let to a single business tenant
A tenant that occupies the premises to run its business, and has control of them, is the responsible person for them. The landlord is responsible for any parts it keeps control of, such as shared stairs or the structure, if the lease leaves them with the landlord.
A block of flats
The freeholder is usually responsible for the structure, external walls and common parts. A management company, a right to manage company, a housing association or a council is responsible for the parts it owns or controls. Each flat is domestic premises, which the Order does not cover, so a leaseholder is not the responsible person for their own flat.
A managing agent
Appointing a managing agent to do the day-to-day work does not move the legal responsibility away from the owner or management company that appointed them. An agent that has control of the building, for example by deciding on fire safety measures and contractors, can also be a responsible person. Enforcement can then be taken against either.
A building with shops, offices and homes
Each business tenant is the responsible person for its own premises. Whoever controls the residential common parts, and the owner for the structure, are responsible for those. Shared escape routes and fire alarms mean each of them needs to know what the others are doing.
High-rise residential buildings of 7 storeys or at least 18 metres also have accountable persons under the Building Safety Act 2022, which is a separate regime from the Fire Safety Order.
When more than one person is responsible
Personal liability
Legal basis
Primary legislation and key regulations