What is compartmentation in fire safety?

Compartmentation is the subdivision of a building into smaller fire-resistant 'boxes' or compartments using fire-rated walls and floors. The goal is to contain a fire in the room of origin, preventing it from spreading and giving occupants time to escape. MPS's penetration sealing services are essential to maintain compartmentation, as even small gaps around pipes can allow smoke to breach the compartment. In more detail: each compartment is enclosed by compartment walls and floors built to a stated period of fire resistance, and in England Approved Document B (Fire Safety) sets out when compartmentation is required and the minimum periods, commonly 30, 60, 90 or 120 minutes depending on the building's use and height. Typical compartment lines separate individual flats, protected escape stairs and lift shafts, different uses within one building (such as a car park beneath residential floors), high-risk plant rooms, and large floor areas that would otherwise be one continuous space. Fire resistance is classified under BS EN 13501-2 against three criteria: R (load-bearing capacity), E (integrity, meaning no flames or hot gases pass through) and I (insulation, limiting the temperature rise on the unexposed face), so a compartment wall might be rated EI 60. Concrete walls and floors perform well in fire in their own right; in practice compartmentation fails at the openings. Every pipe, duct, cable tray and service passing through a compartment wall or floor leaves a hole that has to be fire-stopped with a tested system appropriate to the service, such as intumescent collars or wraps on plastic pipes, fire-rated batts and mastics, or fire-rated mortars, and gaps at wall heads, cavities and risers need cavity barriers. Missing or improvised fire-stopping around services is one of the most frequently reported defects in fire risk assessments, and the Building Safety Act 2022 has brought far closer scrutiny of it in higher-risk residential buildings. Because every new service run creates a new penetration, compartmentation should be re-checked whenever services are added or altered. Where MPS seals a penetration through a concrete wall or floor that forms a compartment line, the seal has to be a tested fire-stopping detail as well as a watertight one.