Protecting data from fire
The current edition of NFPA 2001 outlines the use of clean agent fire suppression systems, which typically are used in buildings such as data centers and mission critical facilities. There are many types of specialty suppression systems including chemicals, gases, oxygen displacement, and others.
- Review codes that drive the design of special suppression systems in various building types.
- Assess the correct suppression system for the application.
Technology and innovation have shifted the way the world does business. The digital age that we live in dictates that we strive to improve efficiency and provide immediate access to information. The advent of the cloud means that information is stored remotely and the livelihood of businesses depend on it. How is all of that information protected? The answer may sound familiar to fire protection engineers (FPEs): it depends. One common method of protection is the use of clean agent fire protection systems.
The most recognized commercial building code in the world is the International Building Code (IBC), which requires buildings over a certain square footage to be provided with an automatic sprinkler system. These systems are designed in accordance with NFPA standards, including NFPA 13: Standard for the Installation of Sprinkler Systems. For unique hazard areas, such as data centers and areas where the application of water is not desirable, IBC provides guidance on the use of alternative suppression systems, with reference to NFPA 2001: Standard on Clean Agent Fire Extinguishing Systems, as well as other NFPA standards. As technology advances, so does the code and relevant design standards, which is why the International Code Council (ICC) and NFPA typically update documents on a regular cycle.
In addition, gaseous systems typically are designed to discharge the entire quantity of agent upon activation. If the fire is not extinguished, the provision of the wet-pipe sprinkler system provides the AHJ with some level of assurance that the fire will not spread to other areas of the building. This may result in certain allowances in code provisions to be impacted if complete protection is not provided.When the building code requires complete protection throughout, some authorities having jurisdiction (AHJs) will require data centers and areas that are storing data to be provided with a sprinkler system regardless of whether an alternative suppression system is proposed, though an alternative system may be more desirable. The reasoning behind that is that once the code requires a building to include sprinkler protection, the entire building must be designed with sprinklers or else it cannot be considered a fully sprinklered building.
A pre-action dry-pipe sprinkler system may be installed in these areas, as the design requirements covered in NFPA 13 consider it an automatic sprinkler system. This system uses a multistep process for fire suppression. First, smoke or heat is identified by the detection system within the room. This action activates a pre-action valve that allows water to flow into the piping, which was previously empty, essentially turning the dry system into a wet system. Second, the heat from a fire causes a sprinkler to actuate, allowing water to suppress the fire. This type of system will not allow water to enter the room unless both steps are completed, preventing unwanted discharge. There are different types of pre-action systems that the FPE can consider, as there is no one-size-fits-all option.
When the AHJ requires some type of sprinkler system, a common approach to protecting these types of areas is to use clean agents in conjunction with a pre-action system. In that instance, it may be prudent to have the smoke-detection system activate the clean agent while also acting as the first action of the pre-action system. That way, the clean agent will discharge and potentially extinguish the fire prior to the fire reaching a point that would activate the heat element on the sprinkler and discharge water onto the expensive computer equipment.
NFPA 2001-2015 outlines the use of clean agent fire suppression systems. The standard contains the requirements for total-flooding and local-application clean agent fire-extinguishing systems. Clean agent is defined in NFPA 2001 as "an electrically nonconducting, volatile, or gaseous fire extinguishant that does not leave a residue upon evaporation." There are a quite a few of different agents that are covered in NFPA 2001—13 to be exact—and each agent has its own unique characteristics and pros and cons of installation. The primary benefit of using a clean agent system is that it does not damage sensitive equipment, as would water.
The design brief
The challenge for the designer or FPE is to try to determine what the best solution is for each unique application. The truth is, there is no "best" agent, although some manufacturers and distributors may lead you to believe otherwise. The best agent will often depend on a number of factors including the desired outcome of the system in place, environmental impact and concerns, quantity of space available for agent storage, and availability of the agent in the region. Coming to an agreement with the relevant stakeholders including the owner, architect, and operations team at the onset of a project will help guide the engineer in the selection of the best clean agent system.
At the onset, it’s critical to understand what the goals are. This is true for any project, so that through implementation there are no surprises and upon conclusion everyone is satisfied with the outcome. By asking the questions upfront, establishing what the expectations are, and determining what the budget is, everyone can walk away knowing the general direction of the project. This is where a client design brief will come in handy, especially when determining protection schemes for sensitive areas.
Set a meeting with the relevant stakeholders so everyone is in the room together. Questions to ask include:
- What are we protecting?
- What is the square footage of the space, and what is the ceiling height?
- What amount of downtime is acceptable?
- Is there space nearby for agent storage?
- As a corporation, is environmental impact important to you?
- Is water an option?
- How important is budget?
- What experience have you had with clean agents in the past? What did you like or dislike?
- If it’s an existing operation expanding, do you have a current service contractor for your systems? If so, are you happy with their service?
Going through this exercise will help establish a baseline of information from which you can then develop a design brief. This essentially is a document that outlines the answers to the above questions and provides the client with the available options for the property. This allows them to make an informed decision rather than having the decision made for them by someone else and then living with the outcomes.
There are differences to each agent, as each has its own benefits and drawbacks. Table 1 outlines some basic characteristics and information for several clean agents covered in NFPA 2001. From the information in Table 1, the engineer can liaise with the client to determine which clean agent is best for the application.
Agents are stored in pressurized cylinders that are kept in a room close to the hazard. Each agent has its own unique characteristics, and the sizes of the cylinders will vary depending on the agent. If, for instance, the client does not want any manmade chemicals or hazardous agents and would prefer to use an agent intended to reduce the oxygen within the enclosure, then an inert gas agent could be a viable solution. Some of the challenges associated with inert gases include a larger footprint required for cylinders and venting of the enclosure because it takes more gas to control a fire.
It’s not always practical to have an engineered clean agent system installed for small data rooms, such as an intermediate distribution frame or main distribution frame that may only include one or two server racks. The infrastructure associated with a clean agent system, including smoke detection, cylinder storage, etc., could leave the owner seeking alternative solutions. What if there was a pre-engineered system that could protect a server rack with something that could be installed in the rack itself, instead of an overhead system designed to protect the entire volume of the room?
There are a couple of different products available on the market that would allow the protection of the server rack by simply installing the system within the rack itself. These systems typically will integrate both a smoke-detection system and clean agent suppression system in a simple modular design that fits within a slot in the server rack. These types of systems may be more suited to smaller applications than the larger engineered-type systems.
There are other applications for pre-engineered systems, including the protection of mechanical equipment and vehicle suppression. If a fire were to occur in a $1 million piece of equipment, wouldn’t it be prudent to extinguish it as quickly as possible? The code would not require a special suppression system for such an application, as this is more of a design option above and beyond what the code would require. Several companies specialize in pre-engineered systems for such applications. Pressurized tubing acts as the means of heat detection within the enclosure. Once the heat is detected, the tubing ruptures to allow the agent to be discharged immediately, extinguishing the fire before an overhead system would have detected it. This type of system also can be used in data center applications, including within the server, below the floor protection, or as a total flooding system for the entire enclosure. Once again, we can see that multiple solutions can be used.
Specialty fire suppression systems are not limited to gaseous and chemical suppression systems. Water can be used to suppress fires in data centers. But you may be thinking, "Isn’t the point to eliminate water from these areas so as not to damage the equipment?" Yes, that is the point. However, there are systems that use water that do not damage the equipment. Water mist is an option for consideration, under the provisions of NFPA 750: Standard on Water Mist Fire Protection Systems. These systems discharge considerably less water than a traditional wet-pipe sprinkler system. Further, it is a green option because there are no manmade chemicals associated with it, so a client wishing to "go fully green" can do so without some of the logistical issues that may arise with other systems.
Another technology that can be used is a hybrid technology that discharges particles comprised of nitrogen and water molecules together. There is minimal residue left after discharge, which extinguishes the fire via heat absorption and oxygen depletion within the enclosure. Droplet size is less than 10 microns and system discharge is typically on the order of about 0.26 gpm (1 l/minute). The system has been proven to be a viable solution for data centers based on these factors and is installed in various locations throughout the world as a result. The use of water on sensitive equipment can be accomplished when using specialty-type systems such as this.
Nicholas A. Moriarty is executive director of fire protection at JBA Consulting Engineers.