Clean-Agent Room Integrity Failure and Manual Door Reliance
A 180 m³ server room is protected by a clean-agent total flooding system using a synthetic halocarbon agent. The room has a raised floor, a suspended ceiling used as a return air plenum, two doorways with 20 mm undercuts, and numerous unsealed cable penetrations. The HVAC system serves the room through four ceiling diffusers and has no automatic shutdown or damper control. The last enclosure integrity test produced a hold time of 2 minutes 40 seconds against a design requirement of 10 minutes. The client has asked whether the system can be accepted with a note that staff will close the doors manually, and whether the existing pressure relief vent is adequate. The cylinder store is outside the room and is air-conditioned.
1. Can the system be accepted with a note requiring staff to close the doors manually? Justify your answer by reference to enclosure integrity, agent retention and life safety.
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No. A hold time of 2 minutes 40 seconds against a 10 minute requirement means the agent concentration will not be retained long enough to reliably extinguish the fire and prevent re-ignition. Manual door closing cannot be relied on: occupants evacuate when the alarm sounds, doors may be propped open for equipment or access, and the HVAC system is still moving air through the room. A note in the documentation does not correct the physical leakage path.
The enclosure is not gas-tight. Door undercuts, unsealed cable penetrations, the suspended ceiling return air plenum and the diffusers all provide leakage. The agent will escape through these paths, and the loss will be worse if the HVAC is running. The room integrity test result is evidence that the design concentration cannot be maintained, so acceptance would undermine the basis of the total flooding design.
There is also a life-safety dimension: staff must not re-enter to close doors during discharge, and the predischarge warning, egress and door release arrangements must be verified. The correct response is to seal the enclosure, address the HVAC, retest, and only then commission the agent system.
2. Prioritise the remediation work and explain how the HVAC and pressure relief vent should be treated.
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First priority is to stop the large leakage paths: seal cable penetrations with approved firestop systems, fit door seals or drop seals to the undercuts, and address the ceiling plenum and raised floor penetrations. The suspended ceiling should not be used as an uncontrolled return air path unless the design explicitly accounts for it and the leakage is controlled.
Second, the HVAC must shut down automatically on agent release and be provided with dampers or motorised shut-off where the ductwork penetrates the enclosure. The four ceiling diffusers should not continue to move air during discharge. The shutdown and damper operation must be part of the cause-and-effect matrix and proven at commissioning.
Third, the pressure relief vent must be assessed after sealing. A room that is too tight can be over-pressured during discharge, damaging walls, ceilings or doors, while an undersized or badly located vent can short-circuit the agent. The vent should be sized for the discharge rate and enclosure strength, located to avoid direct discharge to the outside in a way that harms occupants, and fitted with an appropriate closure. Only after sealing, HVAC control and venting are correct should the room integrity test be repeated. Adding more agent is not a substitute for enclosure integrity.
3. What commissioning and ongoing verification would you require before and after acceptance?
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Before acceptance I would require a successful room integrity test at the design hold time, with the room in its final configuration and the HVAC shut down as it would be during discharge. I would also require verification of detection, predischarge alarm and time delay, agent release, HVAC shutdown, damper closure, door release, pressure relief operation and cylinder valve operation. The as-built enclosure should match the design drawings, including seals and penetrations.
I would check the cylinder store conditions, cylinder weights and pressures, pipework and nozzle layout, and the warning signage and manual release. A discharge test may not be practical, but the sequence should be proven by simulation and component testing, and the room integrity test should be witnessed.
Ongoing verification should include periodic cylinder weighing and pressure checks, inspection of the enclosure for new penetrations or door modifications, HVAC shutdown testing, and a repeat integrity test after any building alteration. Staff training should cover evacuation, the meaning of the alarms, and the prohibition on re-entering to close doors. Any change to the room layout or cabling should trigger a review before the system is relied upon.