Basement car park smoke control failing integrated test

Assessment The system does not meet the approved design basis. Normal-mode extract is 4.6/6 = 77% of requirement, and fire-mode extract is 7.8/12 = 65% of requirement. A 35% shortfall in fire mode is material, and smoke entering the lift lobby shows that the intended pressure and smoke-containment boundary is not working.

The architect’s argument that the lobby is outside the car park is not a sufficient defence: if a fire-rated door opens between the car park and the lobby, smoke can migrate through door gaps, undercuts, or pressure imbalance. The lobby is part of the effective smoke zone unless a validated barrier or lobby pressurisation system prevents ingress.

Additional measurements

• Recheck the actual car park volume used in the ACH calculation; confirm it excludes or includes the ramp correctly.
• Measure fan speed, motor power, and static pressure against the fan curve; check rotation and belt condition.
• Measure duct leakage and damper positions; verify fire dampers are open in test mode.
• Measure make-up air velocity at the ramp and door pressure differentials at the lobby.
• Record CO, temperature, and visibility at multiple points, not just the lobby.
• Verify jet-fan thrust and direction, and the interaction with stair or lobby pressurisation.

Installation defects

• Fan running backwards, incorrect pulley ratio, or VFD limit set too low.
• Ductwork leakage, open access doors, collapsed flexible connections, or fire dampers stuck closed.
• Blocked or undersized make-up path at the ramp, or vehicles/doors obstructing the path during test.
• Jet fans misaligned, reversed, or not operating in the intended zone.

Design and coordination errors

• Fan selected at a duty point that cannot deliver the design airflow against actual system resistance.
• Make-up air path not integrated with the architectural layout; the ramp may be too restricted or doors may be closed.
• No lobby pressurisation or smoke seal; door undercuts and gaps allow smoke to leak into the lobby.
• The smoke zone boundary may not have been coordinated with the architect and fire engineer, so the lobby was not treated as a protected space.

Diagnostic logic If fan power and speed are at design but airflow is low, the problem is system resistance or leakage. If fan speed is low, the control or commissioning is at fault. If airflow is near design but smoke still migrates, the problem is pressure balance and boundary detailing, not extract capacity alone.

Corrective actions

• Do not reduce fan speed. First restore design airflow: correct fan rotation and drive settings, seal ducts, open and lock fire dampers in test mode, and clear the ramp make-up path.
• Rebalance the extract and supply so the fire-affected zone is under negative pressure relative to the lobby and stairs.
• Improve the lobby boundary: seal door gaps, add a lobby pressurisation fan if required by the design, or provide a smoke curtain/vestibule consistent with the fire-engineer’s strategy.
• Recheck jet-fan thrust and placement to keep smoke within the fire zone.

Re-test protocol

• Measure ACH at normal and fire mode with all doors in their normal operating positions.
• Conduct a hot-smoke or approved surrogate test, recording CO, visibility, temperature, and door pressure differentials.
• Demonstrate that the lobby remains tenable and that smoke does not migrate through the fire-rated door.

Interim constraints Until rectified, do not accept the car park for occupancy if the fire strategy depends on smoke control. If partial use is permitted by the authority, impose CO monitoring, restrict vehicle numbers, keep lobby doors closed, and maintain staffed fire watch. The noise complaint must be solved by acoustic treatment, not by defeating the smoke-control design.