Commissioning clean agent fire extinguishing systems
Commissioning of clean agent fire extinguishing systems goes beyond acceptance testing to verify that connected systems accomplish fire protection goals.
By Daniel Kobb, PE, CCRD Partners, Richmond, Virginia
Automatic sprinkler systems are required by building codes in many facilities. While sprinkler systems provide excellent protection for occupants, and preserve the building structure, water-based systems have their limitations. Some facilities include sensitive equipment and contents that would lose significant value if wet. Fire suppression systems that do not use water provide an attractive option. These systems use chemical agents or inert gases to extinguish the fire. Because these fire extinguishing agents do not leave a damaging residue, they are called clean agents.
Clean agents are electrically nonconductive, so they can be discharged to fight a fire without causing additional damage to electronics. They are typically installed in server rooms and data centers where minimizing water damage and downtime after a fire is very important. The agent is generally used in a concentration that is safe for people, so it can be used in occupied areas without threat to the users. Gaseous fire extinguishing systems are designed to quickly put out a fire minimizing the amount of fire and smoke damage to the facility and its contents. This is critical in protecting assets including highly sensitive equipment or property having intrinsically high value such as data, archives, or artwork.
Fire protection systems using clean agents include many components that must be properly designed, installed, and maintained in order for the system to function as intended. Because these systems are far more complex than typical water-based protection systems, clean agent fire protection systems must be commissioned to confirm that the systems function as intended. The systems must be installed properly, be complete, and be functioning. They must be started and operated properly, and the owner must be provided with documentation and training.
In August 2011, the National Fire Protection Assn. (NFPA) published its first consolidated commissioning document, NFPA 3: Recommended Practice on Commissioning and Integrated Testing of Fire Protection and Life Safety Systems. This document represents a big step forward in standardizing the practice of commissioning as applied to the fire protection industry. The NFPA chose to publish this first edition as a “recommended practice” rather than a “standard” to give users and the authorities having jurisdiction (AHJs) the opportunity to work with the document before making it a standard. As a recommended practice it provides guidance in tracking the design and construction process. NFPA 3 takes the user through the following four commissioning steps: planning, design, construction, and occupancy.
NFPA 2001: Standard on Clean Agent Fire Extinguishing Systems includes requirements for testing the clean agent systems. Likewise, other NFPA standards such as NFPA 13: Standard for the Installation of Sprinkler Systems and NFPA 72: National Fire Alarm and Signaling Code include testing requirements for the systems that they govern. But NFPA 3 gives guidance for testing how the various fire protection and building systems are to interact. A new NFPA document, NFPA 4: Standard for Integrated Testing of fire Protection Systems, is under development.
Currently, commissioning and integrated testing is only required by the building codes for smoke control systems. AHJs may sometimes require commissioning of certain building systems, but it’s usually left to owners to make sure that associated fire protection systems work together. Consulting engineers need to help owners identify this necessity and meet it by offering the services of commissioning and integrated testing. With the new NFPA 3 document in hand, we have a tool to provide guidance for how commissioning of fire protection systems should be done.
Together, commissioning and integrated testing can ensure that the fire protection systems can be relied on to protect life and property.
The owner is responsible for the commissioning of the fire protection systems and integration with related systems. The owner usually hires a commissioning engineer and delegates the responsibility for developing and administrating the commissioning process. The commissioning team should be established early and begin work during the planning phase of a project.
During planning, the owner’s project requirements should be created, establishing the owner’s vision for the facility and expectations of how it will be used. This is the time when the commissioning plan should be created, and then it should be continuously updated throughout the design and construction process.
During design, a basis of design should document the concepts used to meet the owner’s requirements and the codes. This includes establishing testing criteria for the fire protection systems. Operation and maintenance documents will be necessary to develop a training program for the operations staff.
System design documentation should include all of the information required for installation, testing, operation, and maintenance of the system. A system manual should include a description of the function and operation of the system, calculations, and any special considerations. It should also provide instructions for installation, maintenance, and inspection.
During construction, submittals should be reviewed for compliance with the basis of design, making sure that the installed systems comply with the contract drawings and calculations, the manufacturers’ instructions, and the codes. As-built drawings should include floor plans indicating dimensions and equipment locations, installation details, schematics, and equipment identification.
The inspection and testing program should include passive fire protection systems in the plan. Perform completion and acceptance testing and check that the fire protection systems comply with the basis of design.
The owner is responsible for the continued performance of the fire and life safety systems, and must see to it that integrated systems are inspected, tested, and maintained according to the commissioning plan. As such, make sure that the owner is trained in the use of the systems, and see to it that the closeout documents are submitted and properly understood.
Testing of integrated systems should be performed to verify that connected systems perform as intended. A narrative should be included in the construction documents to explain the required system interactions. The design should consider the interactions of the systems and include a sequence of operations. In order to provide accountability, specific assignments and responsibilities need to be assigned for testing the systems and their connections.
The finished systems should comply with the owner’s project requirements and the basis of design. Document the testing to verify that the systems operate in sequence. Make sure that the systems have been installed and interconnected according to the manufacturers’ instructions. The as-built drawings must include diagrams that show exactly how the installed systems are interconnected.
Retro-commissioning applies the commissioning process to existing facilities and systems. Acceptance testing has long been practiced, but the concept of commissioning is relatively new to the fire protection industry. Most existing fire protection systems in buildings were not commissioned when installed. In order to provide documented confirmation that the fire protection systems function as intended, a retro-commissioning plan should be developed and executed.
Problems that occurred during the original construction can be resolved through retro-commissioning, and problems that developed during the life of the building can also be addressed. The performance of the fire protection systems is confirmed, corrected, or improved; and documented. The goal is to provide a safe environment that meets the needs of the users, with fire protection systems well maintained by trained personnel.
Most buildings were not commissioned when they were originally constructed, and even if a building was commissioned when it was built, changes can be made over time that might negatively affect the fire and life safety systems’ performance.
Commissioning existing systems may not include bringing them back to their original design. The original design may no longer be relevant to the current use of the facility, or the technology may have changed significantly. The performance objectives of the system must be revised to meet the current and anticipated needs of the users.
The retro-commissioning plan should be developed from a survey and evaluation of installed fire protection and life safety systems design and existing conditions. The team should complete the activities of the normal commissioning process that apply to an installed system. Integrated testing of fire and life safety systems should be performed.
Owners benefit from retro-commissioning of fire protection systems by providing a safer environment for their occupants and an assurance that systems will perform when needed. If the owner follows a regular testing, maintenance, and training program, the insurer may grant lower premiums.
Basis of design
The basis of design describes the decision-making process for the system’s layout, based on the hazard to be protected. When designing clean agent fire extinguishing systems, there are several special considerations.
First, the system must avoid exposing personnel to unsafe levels of the clean agent gas. Design concentrations and exposure times are critical factors, so the system must be coordinated with the building egress design. Occupants are allowed to be exposed to the agent for up to five minutes, but unnecessary exposure to the clean agents must be avoided. Personnel must be evacuated promptly and must be prevented from reentering the protected space during or after agent discharge. The reasons for the evacuation are twofold. First, even though the agent is nontoxic in low doses, it is best to get occupants to a safe area outside of the fire zone. Second, keeping the doors open for too long will reduce the concentration of agent and can diminish its inerting capability. Clearly, training the owner and occupants is a critical component, and a commissioning process is required to ensure that this takes place.
Critical systems are often protected with clean agent fire protection systems. Sometimes uninterrupted protection is required. In these cases, reserve agent supply is permanently connected so that if the system discharges the primary agent supply, the system can be made operational again immediately. More often, a short interruption in clean agent system protection is permissible; however, until a new agent is installed, the area will be unprotected (unless other systems such as sprinklers are provided). The commissioning engineer should confirm and document that arrangements are made for agent replacement.
Most systems use automatic detection and actuation systems to release the agent. A total flooding clean agent system uses open nozzles to distribute the agent throughout the hazard volume. In this way it is similar to a deluge sprinkler system. The agent is held in the storage containers by a normally closed valve or device. In an automatic actuation system, a fire detection system is used to detect heat, flame or smoke, and then causes the valve to open at the proper time. If a new agent system is installed in an area with an existing detection system, the engineer must analyze the existing detection system to ensure that it is operating properly and that it will respond promptly to a fire.
An alarm system is installed with these systems to indicate that there is a hazard to the occupants, or that the system has operated. This alarm must continue until the alarm has been acknowledged, and then the appropriate actions must be immediately taken. Personnel must be trained to respond to an alarm appropriately and must be trained to use manual release and abort switches properly. This must be an ongoing training process, since personnel frequently change. The commissioning engineer must not only verify that such training has taken place once, but that an ongoing program is in place to ensure that future occupants of the hazard area will be trained as well.
Most ventilation systems serving the protected area must be shut down automatically when the fire protection system is activated. The clean agent control panel is connected to the HVAC controls to effect this so that agent is not lost through the mechanical system. The engineer must verify that this system interaction performs properly.
The volume in which a total flooding system is installed must be enclosed to contain the agent. Once the agent discharges, it must be contained at the design concentration long enough to extinguish the fire. Usually this is easier said than done. But it’s a critical consideration—if the agent is not contained, the system will not function as intended.
In new construction it is easier to comply with the requirement that the unclosable openings be kept to a minimum. The structure and walls must be designed to withstand the pressure fluctuations of an agent discharge. Doors, windows, and other openings should be designed to minimize leaks. Ventilation systems should be designed with tightly closing dampers. NFPA 2001 does not require the enclosure to pass an integrity test; however, it does permit the AHJ to require such testing in order to assure performance.
The commissioning engineer should require enclosure integrity testing, especially in the case of an existing facility. Typically, the existing room was not designed to contain clean agent. The engineer must confirm and document that the enclosure functions as required for the clean agent system to perform. Annex C of NFPA 2001 details the recommended test procedure for enclosure integrity. The commissioning engineer administrates this procedure, documents the actions taken to correct deficiencies, and verifies that the test is passed.
The configuration of the protected space should be compared to the design documents. If the volume of the enclosure has changed since the original plan, the intended design concentration will not be met. If the volume of the space has increased, the agent concentration will be too low to be effective. If the volume has decreased, the agent concentration will be too high for safe human exposure.
Agent containers should be located where shown on plans. The containers should be weighed to verify that the fill level is as engineered. Piping should be inspected and tested. The size and configuration of the piping and fittings are critical to ensure even distribution of the agent to all of the nozzles. Nozzles should be located as designed, and nozzle locations should be coordinated with equipment installed in the room. Nozzles should not be located where they will discharge directly on personnel, or send stored items flying.
Detectors should be of the type specified and located as planned. The location of the detectors should be coordinated with the HVAC design so that detection is not hindered by supply air vents or other conditions that might prevent smoke or heat from reaching the detectors in a timely manner. Manual stations should be installed as designed and located for easy access by personnel leaving the room. Their function should be clearly indicated with permanent signage identifying their function.
After construction is essentially complete, the contractor must complete the acceptance steps required in NFPA 2001 to finish the installation of the clean agent system. He or she must notify the AHJ, who may choose to witness the tests. The commissioning engineer should witness and document this testing.
The clean agent system should be inspected and tested by technicians trained by the manufacturer. NFPA 2001 lists the requirements for inspection, testing, maintenance, and training. Test system wiring, and check system controls according to the manufacturer’s instructions. Calibrate and test the fire detection system, and test the releasing circuits. Test the abort switches and manual stations. Manual stations should override the operation of abort switches.
Discharge tests usually are not required nor recommended. These tests have been replaced with pressure and puff tests to check the piping and door fan tests to check the air tightness of the room. Years ago, when discharge tests were required, failure was most often a result of an enclosure that would not contain the agent for the required time.
Essentially, nondestructive tests of all system functions and interactions should be performed, verified, and documented before the system is accepted.
Integrated testing of clean agent systems
Acceptance testing alone may not verify that all of the systems interact with one another in the way that they were intended to. Since a clean agent system will not be effective if this interaction fails, it is imperative that it pass a program of integrated testing to ensure that the systems properly operate together. All interconnected systems must be tested to ensure the proper function of the clean agent system.
The contractor that installs the clean agent system might be contracted only to perform acceptance tests on the clean agent system. It is up to the commissioning engineer to ensure that the interface between the systems, and the overall function of the fire protection systems, work as planned. As such, the coordination of the subcontractors required to test multiple systems simultaneously is an important task.
When an owner recognizes the need to commission the fire protection systems in its facility, the specifications should identify the important interfaces between systems. The design requirements should include a description of proper interaction of the fire protection systems and features of the building. System interconnections should be specified to ensure that they are compatible and operate properly. Define who is responsible for what tests, and when multiple contractors are required to perform interactive testing.
After all of the integrated systems have passed the tests, obtain a certificate of inspection signed by the contractor and the AHJ.
Clean agent systems involve many component systems that must interact as designed to protect life and property. The challenges mount when commissioning an existing system or installing a new system in an existing building. A well-executed commissioning program goes beyond acceptance testing to make sure that all interconnected systems work together to accomplish the fire protection goals.
Kobb is a professional fire protection engineer on the life safety team at ccrd partners. He engineers a variety of fire and life safety systems for sectors including universities, healthcare, and airports.