Does a fire strategy tell you which smoke control products to buy?

Almost never. A fire strategy sets objectives and performance requirements: which spaces are protected, how the building is evacuated, what free area or extract rate each space needs, and what fire resistance the boundaries must hold. It stops short of naming products because product selection is a contractor and supplier responsibility. The strategy gives you the numbers and the classifications; you turn those into an equipment schedule and check every declared performance back against the document.

What is the difference between a prescriptive and a performance-based fire strategy?

A prescriptive strategy follows the published guidance directly, using the free areas, shaft dimensions and travel distances set out in Approved Document B, BS 9991:2024 or BS 9999. A performance-based strategy departs from that guidance and justifies the departure by fire engineering analysis, usually CFD modelling of the actual geometry. The practical difference is how much room you have to substitute. Under a prescriptive strategy you can swap a product for any equivalent that meets the same stated figures. Under a performance-based strategy the modelled inputs are the specification, and changing one invalidates the analysis until the fire engineer reruns it.

What should you ask the fire engineer before ordering smoke control equipment?

Ask whether the design is prescriptive or CFD-justified, and if it is CFD-justified, ask for the modelled inputs: vent aerodynamic free areas, fan volume flow rates and static pressures, damper positions and leakage classes. Ask for the required fire resistance of every element the equipment penetrates, the damper classification string that follows from it, the fan temperature and duration class, the required standby power duration, and the cause and effect matrix. Ask who signs off any substitution. Get the answers in writing before the order goes in, not after delivery.

Can you change a vent or fan specified in a fire strategy for a cheaper equivalent?

Only if the replacement meets or exceeds every performance figure the strategy relies on, and only with the fire engineer's agreement in writing. The trap is aerodynamic free area. Two vents with the same overall size can have very different aerodynamic free areas depending on blade geometry, so a like-for-like swap on physical dimensions can quietly cut the ventilation performance the strategy assumed. Any substitution also has to be recorded in the as-installed information, because the golden thread has to reflect what is actually on site.

Fire Strategy to Smoke Control Specification

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Publishing Sunday 8 November 2026

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How to turn a fire engineer's strategy into a buildable smoke control specification: what to extract, what you can change, and what to ask before ordering.

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