Compartmentation is the building holding fire in the room it started in for long enough that everyone else can leave or stay put safely. It is walls, floors, doors and the seals around everything that passes through them. It is invisible when it works, it is destroyed by ordinary trades doing ordinary work, and it is the single most consequential thing a fire risk assessment can find wrong.
How compartmentation gets broken
Not by fire. By a data cable pulled through a compartment wall above a ceiling tile and never sealed. By a plumber coring through a floor. By a riser cupboard left with a hole where a pipe was removed. Every trade that works in a ceiling void can break it, none of them is usually told that the wall is a compartment wall, and nobody inspects the void afterwards. That is why buildings that were compliant at handover are not compliant ten years later.
What a fire compartmentation survey actually does
Opens up. A compartmentation survey that does not lift ceiling tiles and open risers has inspected the parts that were never the problem. The surveyor identifies the compartment lines from the fire strategy or the drawings, follows them through the building, and records every breach with a location, a photograph and a remedy. The deliverable is a schedule of defects somebody can price and fix, not a narrative.
The products, and why a passive fire protection system is tested as a whole
A firestopping system is tested as a whole: this sealant, in this thickness, around this service, in this substrate. Intumescent products expand under heat to close the gap a burning plastic pipe leaves behind. Fire batt, collars, wraps, pillows and mastic each have a tested application. Using the wrong one, or the right one incorrectly, produces a seal that looks finished and performs for minutes rather than an hour.
Compartmentation fire dampers, which have moving parts
Where ductwork passes through a compartment wall a fire damper closes it. It has moving parts, it sits inside a duct where nobody can see it, and it is routinely found seized or painted open. Access hatches are needed to test them, and buildings without those hatches cannot demonstrate that their dampers work at all.
Why it decides the evacuation strategy
A stay put policy in a block of flats is a promise that fire in one flat will not reach the next one before it is out. Compartmentation is the entire basis of that promise. Where a survey finds it breached, the honest response is an interim measure, often a waking watch or a common alarm and simultaneous evacuation, until the work is done. That is the connection between a ceiling void nobody looks at and a decision about how a building is occupied.
Questions people ask about compartmentation survey
What is fire compartmentation?
Dividing a building with fire resisting walls and floors so fire and smoke are contained for a period, protecting escape routes and other occupants.
What does a fire stopping survey involve?
Identifying the compartment lines and inspecting them, including opening ceiling voids and risers, then recording every breach with a location, evidence and a remedy.
Is firestopping a legal requirement?
The Fire Safety Order requires general fire precautions to be adequate and the premises to be maintained. Where a building relies on compartmentation, keeping it intact is how that duty is met.
Why does compartmentation affect stay put?
Because stay put assumes fire stays in the flat of origin. If compartmentation is breached, that assumption fails and the evacuation strategy has to change until it is restored.
How are fire stopping products chosen?
By the tested system, not by the product on its own. A sealant, a collar or a batten is tested in a specific construction with a specific service passing through it, and using it anywhere else leaves you with a product that has evidence for a detail you do not have.
What is passive fire safety?
The part of the protection that is built in and does nothing until there is a fire: compartment walls and floors, fire doors, the sealing where services pass through, and dampers in ductwork. It is what holds a fire in the place it started for long enough for the active measures and the escape plan to work.