Where Are They Used?

Mechanical systems are often used when: Extended corridors / dead-end travel distances: When common corridors are long, MSVS is often the right choice.

Published guidance caps dead-end travel distance at ~30 m when the corridor is protected by a suitable mechanical shaft system (measured from the stair).

By contrast, natural solutions are typically used where dead-end distances are short—~7.5 m (up to ~15 m with sprinklers)

Limited façade/roof openings: Deep plans, internal corridors, basements or atria where natural (AOV/NSHEV) can’t achieve the free area or aerodynamic performance needed.

Predictability is critical: Sites exposed to adverse wind/stack effects where natural systems would be unreliable; MSVS gives controlled, repeatable extract rates.

Long/complex escape routes: Extended or convoluted corridors where you need zoned extract to keep escape paths tenable and aid firefighter access.

Tight shafts/retrofit constraints: When existing shaft sizes are small, MSVS (fans + dampers) can often deliver the required performance with smaller ducts/shafts than natural systems.

Basements & enclosed car parks: No viable natural path for smoke/heat—mechanical extract is typically required.

Zoning & containment: You need floor-by-floor or zone control (dampers, smoke shafts) to prevent smoke migration beyond the fire floor.

Dual-use needs: Where the design calls for day-to-day environmental corridor ventilation (with correct cause-and-effect so life-safety takes priority during fire).