Fire compartmentalization in utility buildings: the complete guide

Compartmentation is one of the most fundamental principles of passive fire protection: by dividing a building into fire compartments and, where necessary, sub-compartments, a fire stays confined to where it started for longer and escape routes hold out longer.

In this guide you will read what a fire compartment is, how large it may be, how compartmentation works for each type of non-residential building and where it most often goes wrong in existing buildings.

What is a fire compartment?

A fire compartment is the area within which a fire must be contained. The separations around it, meaning the walls, floors, doors and everything that passes through them, must hold back the fire for a minimum time. That time is called the WBDBO, the resistance to fire penetration and fire spread. For new construction it is generally at least 60 minutes between two fire compartments. Other levels apply to existing buildings and renovations; see WBDBO explained.

Smaller units can lie within a fire compartment. A sub-compartment, such as a dwelling, further limits the spread of fire. For residential and care functions, among others, requirements apply to protected sub-compartments. In addition, the Bbl sets requirements for resistance to smoke passage, for example around escape routes. The term ‘smoke compartment’ comes from older regulations.

How large may a fire compartment be?

That depends on the use and on whether it is new construction or an existing building:

Larger compartments occur in industrial halls and distribution centres. They require an equivalent level of fire safety, for example substantiated in accordance with NEN 6060 (controllability of fire) or NEN 6079. Usually the municipality, as the competent authority, assesses such a solution, with advice from the safety region. The Informatiepunt Leefomgeving gives an overview of the rules for fire compartments in new construction.

If a large compartment is later divided or used differently, for example a storage hall that partly becomes office space, the compartmentation plan must be reviewed again.

The building blocks of compartmentalization

• Walls and floors with the required fire resistance duration
• Doors and frames that separate compartments, often self-closing
• Seals around cable, pipe, and duct penetrations
• Fire dampers in ventilation ducts that cross compartment boundaries
• Connections above ceilings, such as a continuous wall or a fire-resistant ceiling, as part of a substantiated compartment boundary

Together, these components must deliver the required WBDBO. NEN 6068 looks at all routes, and the route with the lowest resistance is decisive: a 60-minute wall with one open cable penetration does not achieve 60 minutes.

Compartmentation by building type

• Offices: each floor often forms its own fire compartment. Critical points are shafts, cable trays through walls and suspended ceilings that run across a separation.
• Shops and shopping centres: sales floors are separated from storerooms, technical rooms and stairwells. Every fit-out by a tenant creates new penetrations.
• Schools: classrooms, corridors and stairwells together form a plan centred on safe escape routes. Work is usually scheduled during the holidays.
• Industrial halls and distribution centres: large compartments with fire walls between the hall, offices and technical rooms, and protection of the steel structure where it must keep carrying its load.

Shafts, ceilings and façades: the hidden routes

Fire and smoke take the path of least resistance, and that rarely runs through the wall itself. In practice, things go wrong in three places:

• Shafts and service ducts. A shaft that runs over several floors must be sealed at each floor or itself be built as a fire-resistant duct.
• Spaces above ceilings and under raised floors. If a compartment wall stops at the suspended ceiling, fire can pass over it unhindered. The compartment boundary must demonstrably continue above a suspended ceiling as well. Whether a continuous wall, a fire-resistant ceiling or another construction is suitable depends on the required performance and the substantiation of the complete connection. A fire barrier curtain is not automatically sufficient.
• Façades. Fire can spread along the outside of the building to the floor above. That route also counts towards the WBDBO.

Common mistakes

In practice, we regularly see the same recurring problems:

• Penetrations that were not resealed after a renovation
• Fire doors permanently fixed open with a wedge or hook
• Suspended ceilings above which the compartment boundary does not demonstrably continue
• Lack of maintenance causing seals to become outdated or damaged over the years

Keeping compartmentation up to date in an existing building

In a building that is in use, compartmentation is not a one-off achievement. Every change of tenant, every new cable and every installation project can breach a compartment boundary. Three measures keep it in order:

1. An up-to-date compartmentation drawing, showing every fire separation and the required WBDBO.
2. A fixed protocol for new penetrations: whoever makes an opening has it sealed with a system that falls within the substantiated field of application, and records it.
3. Periodic inspection, with every seal recorded in a logbook.

Designing compartmentalization: where to start

A good compartmentalization plan starts with a clear division of the building into logical fire compartments, tailored to the use function, escape routes, and the installations present. Our consultancy and assessment service is often the first step in this process.

Frequently asked questions