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Special Hazard Room Design Checklist for Clean Agent and Inert Gas Systems

If your room is protected by a gaseous fire suppression system, clean agent or inert gas, this checklist helps you prevent the failures that show up during acceptance testing or, worse, during a real discharge. Use it during design, construction, and renovations to keep the enclosure tight, control airflow, and ensure the suppression sequence works as intended.

1) What This Checklist Is

This is a practical, project-ready checklist for special hazard enclosures protected by gaseous suppression. It is designed to align the building envelope, HVAC, electrical interfaces, and detection and releasing controls so the room can hold agent concentration and the system can discharge safely and effectively.

If you want the full engineering overview that this checklist is based on, start with SSI’s main guidance page: Design Considerations for Special Hazards.

2) How Gaseous Special Hazard Systems Fail in the Real World

Most special hazard system issues are not “bad agent” problems. They are coordination problems. The suppression system can discharge perfectly and still fail to control the fire if the room cannot hold concentration or if HVAC keeps moving air like nothing happened.

The top failure modes SSI sees

• Unsealed penetrations, cable trays, conduit, pipe chases, and wall joints that leak agent out of the room.
• Return air plenums, economizers, and make-up air paths that remove agent before it can work.
• Doors without sweeps or automatic closers, or doors propped open during discharge events.
• No dampers, wrong dampers, or dampers not interlocked to the releasing sequence.
• Control interfaces not defined early, resulting in late rework for EPO, HVAC shutdown, smoke control, and building fire alarm signaling.

If your goal is to improve room tightness, start with SSI’s sealing guidance: Proper Sealing of Clean Agent Rooms and Room Integrity Testing and Sealing.

3) Checklist, Architecture and Enclosure Integrity

Your “room” is not just walls and a door. It is an engineered enclosure. If the barrier stops at a drop ceiling, or if the space shares a return plenum with the rest of the building, you do not have a reliable enclosure until you fix it.

Enclosure construction and leakage control

• Walls extend to a solid barrier, ideally to the structural deck or an equivalent continuous construction plane.
• Penetrations are sealed, including conduit, cable tray, sleeves, ducts, piping, and abandoned openings.
• Doors have perimeter seals and sweeps, and are self-closing where appropriate to prevent leakage during discharge.
• Raised floors and subfloors are properly zoned and bulkheaded where required to prevent agent bypass and uncontrolled migration.
• Above-ceiling spaces are treated intentionally, especially if used as a return air plenum.

Practical questions you should answer before construction finishes

• What is the exact protected volume, including subfloor, above-ceiling, and soffits that are inside the enclosure boundary.
• Where can agent leak out, and what trade owns each seal, electrical, low voltage, mechanical, or general contractor.
• Will the room be renovated frequently, and how will sealing be maintained when cable additions occur.

4) Checklist, HVAC and Airflow Control

HVAC is the part that most often defeats clean agent performance. If airflow keeps moving during and after discharge, you can dilute concentration, move agent away from the hazard, or exhaust it out of the enclosure.

HVAC shutdown and damper coordination

• Identify all supply, return, relief, and exhaust paths that connect to the protected enclosure, including above-ceiling plenums and shaft paths.
• Define which paths must shut down on second alarm, and which must remain on for life safety or smoke control, if applicable.
• Install motor-operated dampers where needed and interlock them to the releasing sequence so the enclosure can hold agent.
• Account for CRAC units, economizers, and make-up air systems that can silently defeat concentration if not controlled.
• Plan post-discharge purge and exhaust sequencing deliberately so you do not remove agent too quickly.

Common HVAC mistakes that show up late

• Using above-ceiling as a return plenum without a defined clean agent boundary and shutdown strategy.
• No clear “owner” of damper controls, resulting in dampers installed but not powered, not wired, or not programmed.
• Late changes to HVAC that add new leakage paths, such as new penetrations, ductwork, or relief air connections.

5) Checklist, Electrical Interfaces and Control Integration

Special hazard protection is a sequence, not a cylinder. The releasing panel must coordinate with building fire alarm, HVAC shutdown, emergency power-off, and any site-specific interlocks required by code, owner standards, or AHJ direction.

Power and control basics to verify early

• Dedicated, reliable power is provided for releasing control equipment, detection power supplies, and any supporting devices required by the system design.
• All required dry contacts and signals are defined in writing, including what triggers shutdowns and what reports to the building system.
• Interfaces are in the correct enclosures and electrically separated where required, rather than being improvised inside the releasing panel.
• Emergency Power Off, when required by the facility, is tied into the suppression sequence correctly and tested as part of acceptance.

Detection and releasing coordination

• Detection layout matches the hazard, airflow patterns, and obstructions, including containment zones in modern data centers.
• Releasing logic and delays reflect the operational risk profile of the room and the life safety strategy for occupied spaces.
• If aspirating detection is used, verify placement, sampling points, power, and interface requirements, see VESDA aspirating smoke detection.

If you need detection options for special hazards, see SSI’s fire alarm and detection resources: Fire Alarms and Detection Systems.

6) A Practical Sequence of Operation You Can Use for Coordination

Your project needs a written sequence of operation that every trade can build around. Below is a practical framework. Final sequence should be engineered to your hazard, occupancy, and AHJ requirements.

1. First alarm: detection initiates local notification and supervisory actions per design, no discharge.
2. Second alarm: releasing sequence begins, discharge timer and pre-discharge notification activate as required.
3. HVAC actions: supply and return shutdown and dampers close as defined to contain agent within the enclosure.
4. Interlocks: EPO, equipment shutdown, and other owner required interfaces activate according to the designed logic.
5. Discharge: agent releases through engineered nozzle network within the required discharge window.
6. Post-discharge: hold time is preserved to prevent re-ignition, then purge or exhaust operates per engineered plan and local requirements.
7. Reset and return to service: system is inspected, cylinders are verified, and room integrity is confirmed before full return to operation.

7) Acceptance Testing and Commissioning Readiness

Acceptance testing failures are usually preventable. The purpose of commissioning is to prove that the enclosure, controls, and suppression equipment work as a complete system, not as disconnected parts.

Commissioning readiness checklist

• As-built drawings reflect actual penetrations, dampers, and device locations, not the original plan set.
• All shutdowns and interlocks are programmed, powered, and tested, including damper closure confirmation where used.
• Nozzle locations match the engineered design, and piping is installed per the final hydraulic calculations.
• Room boundary is finalized and sealed, including doors, penetrations, and any subfloor or above-ceiling boundaries.
• Room integrity testing is planned when required by the project, AHJ, or owner standard, see Room Integrity Testing and Sealing.

For clean agent system fundamentals and where they fit, see: Clean Agent Fire Suppression and for inert gas considerations, see: ProInert2 Inert Gas Fire Suppression.

8) Renovations, Retrofits, and Changes After Commissioning

Special hazard rooms rarely stay static. Cable additions, new penetrations, plenum changes, and equipment swaps can quietly reduce enclosure integrity and change airflow. The common failure is assuming the room is still “good” because it was good at turnover.

Change management rules that protect performance

• Any new penetration gets sealed immediately, no exceptions, no “later.”
• Construction scope near the enclosure triggers a room integrity review.
• Major HVAC, ceiling, plenum, and cable infrastructure changes trigger re-testing when required by policy or best practice.
• Service records and as-builts stay current so troubleshooting is fast when something changes.

SSI’s sealing guidance is built for exactly this problem: Proper Sealing of Clean Agent Rooms.

9) FAQ, Special Hazard Design Questions People Actually Search

What are the room requirements for a clean agent system

The room must behave like a controlled enclosure. That means continuous barriers, sealed penetrations, doors with seals, defined above-ceiling and subfloor boundaries, and HVAC controls that prevent agent from being removed during the hold period. Start with SSI’s main engineering overview: Design Considerations for Special Hazards.

Do I need dampers for clean agent rooms

If your HVAC paths can carry agent out of the protected volume, dampers and shutdown logic often become necessary to contain agent, especially when above-ceiling is used as a return air path. The correct approach depends on how the room is constructed and how air moves through it.

What is room integrity testing and why does it matter

Room integrity testing evaluates how well the enclosure can hold agent concentration. Many owners use it to validate enclosure readiness and reduce uncertainty before a discharge event. Learn more: Room Integrity Testing and Sealing.

Which system is better for special hazards, clean agent or inert gas

It depends on hazard class, occupancy, environmental priorities, and room constraints. SSI designs both clean agents and inert gas and helps owners choose based on performance requirements and lifecycle planning. Compare options here: Clean Agents and ProInert2.

10) Why SSI for Special Hazard Design and Execution

SSI has been engineering and supporting special hazard fire protection since 1983. The difference is coordination. SSI helps align architecture, mechanical, electrical, detection, and suppression so you are not trying to solve system-level failures at the end of a project.

• Special hazard design support across clean agents, inert gas, CO2, and specialty water solutions.
• Project coordination guidance so trades know what must happen before acceptance testing.
• Ongoing service to keep rooms reliable through renovations and equipment changes, see Service and Maintenance.

Codes and Standards Reference

Special hazard designs typically reference multiple standards and local code requirements. Confirm your exact code path with the AHJ and project engineer of record.

• NFPA 2001, Clean Agent Fire Extinguishing Systems
• NFPA 72, National Fire Alarm and Signaling Code
• NFPA 75, Fire Protection of IT Equipment

Service Area Focus

SSI is headquartered in Breinigsville, Pennsylvania and supports special hazard projects across the East Coast region within practical response distance, including Pennsylvania, New Jersey, New York, Delaware, Maryland, and surrounding areas. If you operate multi-site facilities, SSI can help standardize enclosure readiness, commissioning expectations, and long-term maintenance practices.

Related SSI Pages

• Design Considerations for Special Hazards
• Clean Agent Fire Suppression
• Proper Sealing of Clean Agent Rooms
• Clean Agent Room Integrity Testing and Sealing
• SF-1230 / FK-5-1-12 Clean Agent Systems
• FM-200 Clean Agent Systems
• ECARO-25 Clean Agent Systems
• ProInert2 Inert Gas Fire Suppression
• Fire Alarms and Detection Systems
• Service and Maintenance

Suppression Systems, Inc., 155 Nestle Way, Suite 104, Breinigsville, PA 18031.