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Design Considerations for Special Hazard Fire Suppression

Engineering the right clean agent system starts long before a cylinder arrives on site. Special hazard environments such as data centers, control rooms, archives, and laboratories require careful attention to architecture, HVAC, power, and codes so the system performs as designed when it matters most.

In an effort to assist our customers with preparing an area for a clean agent fire suppression system, SSI has developed these practical design considerations for special hazards. Our customers have found them helpful when planning and constructing an area that will be protected by systems such as FK 5 1 12 clean agents, ProInert2 inert gas, ECARO 25, and FM 200.

Step One, Understand The Hazard You Are Protecting

Every design starts with a clear definition of the hazard. The type of fuel, room use, occupancy, and criticality all influence which agent and design approach are appropriate.

  • Class A hazards, ordinary combustibles such as paper, cardboard, cable insulation, furniture, and building finishes.
  • Class B hazards, flammable and combustible liquids such as fuels, lubricants, and some process chemicals.
  • Class C hazards, energized electrical equipment such as server racks, UPS systems, motor control centers, and process controls.

Hazard classification drives the design concentration and the choice between chemical clean agents and inert gas systems. For an overview of common clean agents that SSI designs, visit our Clean Agent Fire Suppression page.

Architectural Considerations, Building The Right Room

Room integrity is one of the most critical and often overlooked parts of any gas system design. A clean agent or inert gas system can only work properly if the protected enclosure can hold the agent long enough to interrupt the fire and prevent re ignition.

Architectural Checklist

  1. The perimeter walls of the room should be full height, extended to the structural deck or next solid barrier, not stopping at a drop ceiling.
  2. With subfloor applications, bulkheads shall be installed to properly isolate the suppression zones and prevent agent from bypassing the protected volume.
  3. The access doors to all protected areas should have door seals and sweeps as well as automatic door closures to limit leakage during a discharge.
  4. Any penetrations to the exterior walls for cables or conduit should be sealed using appropriate firestopping or sealing materials.

For a deeper look at why enclosure tightness matters, review our dedicated guidance on Proper Sealing of Clean Agent Rooms.

Mechanical Considerations, HVAC And Airflow Control

Mechanical systems directly affect whether a clean agent discharge will stay in the room long enough to be effective. Conditioned air and return paths must be controlled so they do not carry agent away from the hazard.

Any supply or return air from the building system should have motor operated dampers for closure upon the control system second alarm. These are necessary to help contain the agent within the hazard in the event of a discharge. The dampers become extremely important when the above ceiling area is used as a return air plenum, which is tied into the building air system.

  • Coordinate damper locations and control wiring with the fire suppression control panel during design, not after installation.
  • Consider the impact of dedicated computer room air conditioning (CRAC) units, economizers, and make up air systems.
  • Plan for post discharge exhaust or purge systems if required by local codes or owner standards.

Electrical Considerations, Power And Control Interfaces

Electrical design is more than just running power to a control panel. Proper interconnection between suppression controls, HVAC, emergency power off, and life safety systems is essential for safe and code compliant operation.

  1. If electrical power to computer equipment is required to have an emergency power off switch, it shall be tied into the control panel via a dry contact so that power can be removed as part of the suppression sequence.
  2. The dedicated air unit and any dampers should be interconnected for shutdowns with the control panel. All power for these interconnections shall be independent of the control panel and located within their own enclosures.
  3. A 120 VAC power circuit will have to run through a dedicated 20 amp circuit breaker to the releasing control panel, pre action air compressor, and VESDA power supply where applicable.
  4. Typically, an interconnection between the control panel and the building life safety system is required by local codes so that alarms, supervisory signals, and system troubles are reported correctly.

When integrating advanced detection technologies such as VESDA aspirating smoke detection, SSI coordinates detector placement, power requirements, and signal interfaces with the fire alarm and suppression systems.

Unique Design Considerations For Modern Facilities

Many special hazard rooms now include features that did not exist when traditional clean agent rooms were first defined. These features have a direct impact on how gas fills a space and how long it will remain at the required concentration.

  1. Hot aisle and cold aisle containment areas in data centers, which change airflow patterns and may create partial barriers inside the protected volume.
  2. External humidification systems that introduce additional penetrations or airflow into the room.
  3. Continual mixing or HVAC systems that run continuously, which can dilute agent if they are not properly shut down on release.
  4. Exhaust purge systems that must be sequenced carefully so they do not remove agent too quickly after discharge.

SSI reviews these unique features during the early design phase so that suppression performance, detection layout, and mechanical controls all work together.

Calculating Agent Quantities, Volume, Environment, And Safety

Clean agent and inert gas systems are engineered solutions. Each design is based on a detailed calculation of agent quantity, nozzle layout, and discharge time according to manufacturer data and NFPA 2001.

  • Room volume, length x width x height, adjusted for mezzanines, subfloors, soffits, and significant solid obstructions.
  • Altitude and temperature, agent performance and storage pressure can change with elevation and ambient temperature conditions.
  • Design concentration, percentage by volume required for the specific clean agent and hazard class.
  • Occupancy safety, ensuring designs stay within NOAEL and LOAEL guidance for occupied spaces.

Engineered ECARO 25 clean agent cylinder bank for special hazard protection

SSI uses manufacturer approved software, hydraulic flow tools, and decades of field experience to size cylinder banks, similar to the ECARO 25 system above, so that the correct amount of agent reaches every nozzle in the required time window.

Piping And Hydraulic Flow, Delivering Agent Where It Is Needed

The piping network is the highway that delivers agent from the cylinders to the hazard. Proper hydraulic design ensures that the farthest nozzle receives the correct flow within the required discharge time.

  • Clean agent systems are typically designed for a discharge time of 10 seconds, while inert gas systems often use a longer discharge window according to applicable standards.
  • Pipe sizes, fitting types, and elevation changes all affect pressure loss and flow, and must be accounted for in design calculations.
  • Nozzle locations and orifice sizes are selected to provide uniform agent distribution without causing excessive noise or drafts that could disturb sensitive equipment.

For projects that are also evaluating inert gas or water based specialty systems, see our pages on ProInert2 Inert Gas Fire Suppression and Specialty Water Suppression Systems.

Codes, Standards, And Industry Guidance

Special hazard fire suppression designs must comply with multiple codes and standards. SSI designs systems to the latest editions of applicable NFPA standards and manufacturer manuals.

For projects that involve legacy HFC based systems, SSI also tracks regulatory changes under the American Innovation and Manufacturing Act. You can learn more on our AIM Act and HFC Phasedown overview page.

SSI remains connected to broader industry guidance through organizations such as the Fire Suppression Systems Association (FSSA) and resources from agencies including the United States Environmental Protection Agency and National Institute of Standards and Technology fire research.

Why Partner With Suppression Systems, Inc. For Special Hazards

Fire protection is important to your business. Finding the right solutions to your fire protection needs is something we have been doing since 1983. Our customers have found that they can trust the experience, knowledge, honesty, integrity, and ethics of the SSI team.

  • NICET certified designers and project managers focused on special hazards.
  • In house CAD, hydraulic modeling, and agent flow calculations.
  • Experience with clean agents, inert gas, carbon dioxide, and specialty water systems.
  • Support for both new construction and retrofits of existing systems.
  • Coverage across Pennsylvania, New Jersey, New York, Delaware, Maryland, and surrounding regions.

We invite you to contact one of the members of our team with your questions or to discuss how SSI can protect your employee life safety and your valuable assets for the continued operation and success of your company. To take the next step, visit our Contact Us page or call 1 800 360 0687 to speak with a system sales and design consultant about your special hazard.

Great Knowledge, Great Service, It Is That Simple

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

Toll Free, 1 800 360 0687
Phone, (610) 709 5000
Fax, (610) 709 5001
Email, info@suppressionsystems.com

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