Clean Agents Protect Data Centers From Fire
New systems help reduce downtime
THE HIGH COST OF DOWNTIME
Figure 1. Cost of data center downtime for an unplanned one-hour outage
There was a time when temporary business interruptions were a minor and relatively inexpensive inconvenience to operations. With modern reliance on the interconnected global IT infrastructure, loss of IT service often has a dramatic effect well beyond the affected business, impacting clients, suppliers, whole industries, and society at large. A recent Ponemon Institute survey on data center outages estimated that the revenue lost during a one-hour business interruption would exceed $50,000 for a third of the businesses surveyed, and, some respondents estimated losses in excess of $1 million (see figure 1)! The total cost of downtime is not limited, however, solely to monetary costs but includes loss of reputation, customer confidence, loss of employee productivity, and costs related to remedial actions. In addition, for many businesses new federal regulations require data to be current, accessible, and searchable at all times. Downtime may also put a business in violation of federal regulations, leading to potential lawsuits, costly audits, and fines.
Data center fires typically involve wiring, power distribution components, and various types of IT equipment and can occur throughout the data center. For example, the University of North Carolina Greensboro traced a fire at one its data centers to a single overheated server.
Data center fuel loads consist primarily of the combustible plastics comprising the IT equipment, power cables, and airflow containment systems; they also include additional Class A materials such as data storage media and paper. Computers and electronic equipment are particularly sensitive to fire-related damage (see figures 2 and 3). Thermal damage of electronic components occurs at relatively low temperatures (see table 1), and combustion products, smoke, and soot from a fire often cause as much or more damage to electronic equipment than heat. Hard drives are particularly sensitive to contaminants, with malfunctions occurring with particles as small as 0.5 microns. The deposition of conductive and non-conductive soot can also result in circuit shorts and interruptions, respectively. These deposited coatings can be difficult to completely remove, creating future reliability issues, disruptive faults, and ghost errors that can be very hard to discover.
Table 1. Thermal damage onset (Robin, M.L. and Scott A. Craig, “Fire Protection for Computer Rooms,” Fire Protection International, August 2003.
The high value and sensitivity of the electronic equipment found in data centers, combined with the consequences of system interruption, makes fire protection a critical component of any data center risk assessment. While some facilities surprisingly choose not to provide fire suppression capability, most choose between a water system and a clean agent gas system.
The primary objective of a sprinkler system, whether wet pipe or pre-action, is not fire extinguishment but fire control: confining a fire to its point of origin and controlling ceiling temperatures to prevent structural damage and fire spread. Sprinkler systems use water, which has obvious disadvantages around electronics and electrical systems. In the event of activation, water damage to the facility and equipment can be substantial, often worse than the fire damage itself, and the cleanup required after sprinkler system activation can be extensive. Sprinkler heads include a thermally sensitive frangible bulb or a fusible link, which release water only after the head reaches a preset minimum, temperature, usually 135°F. By this time fires are well developed and can cause considerable direct fire, smoke, and water-related damage (see figure 4). The extensive cleanup after a sprinkler system discharge, and resulting business interruption, will likely add to the business cost of a fire. For these reasons sprinkler systems are best suited for the protection of structures not for the protection of critical assets located within those structures.
Water-mist systems are a more recent entrant into the fire-suppression area. Such systems generally require high-pressure pumps and special nozzles to distribute a fine water mist into the protected space. Water mist primarily extinguishes via oxygen dilution: steam produced from the mist near the fire displaces oxygen and puts out the fire. Water mist systems perform well on large energetic fires, but have exhibited poor performance on small fires. Water mist, like water, does not fully flood a space and as a result is not suitable for extinguishing hidden or obstructed fires, such as an in-cabinet or in-rack fires. While lesser in volume than sprinklers, residual water from these systems following system discharge is enough to necessitate cleanup and interrupt service. Potential water damage to electronics and the incompatibility of water and electricity remain a concern. For these reasons water-mist systems, like sprinkler systems, are not recommended for the protection of high-value electronic assets and services located within a structure.
Table 2. Commercially available clean agent options for data and telecommunication facilities.
Table 3. Clean agents compared.
The primary objective of a clean agent system is to extinguish fires quickly. Clean agent systems combine rapid detection and rapid agent discharge to extinguish fires in their incipient stage, significantly reducing asset damage due to thermal effects or fire combustion products, allowing facilities to quickly return to service after a fire event. Further, clean agents do not leave corrosive or abrasive residues following their use, eliminating the cost and need for cleanup as well as the potential for longer-term equipment operational issues. A gaseous clean agent penetrates into hidden or obscured areas and densely packed cabinets and racks—common sources of IT fires. Consequently, clean agent systems are ideally suited as the first line of defense to protect electronic equipment in mission critical facilities.
The ideal extinguishing agent for the protection of data center equipment has the following characteristics:
• Clean (no residue)
• Proven, high extinguishing efficiency for types of fires expected (Classes A, B, and C)
• Low chemical reactivity
• Long storage stability
• Low toxicity
• Low environmental impact
• Cost effectiveness
• Wide commercial availability
|Figure 2. Smoke and fire damage||
Figure 3. Smoke and fire damage
Currently three broad classes of clean agents are commercially available: inert gases, hydrofluorocarbons (HFCs), and perfluoroketones (see table 2).
Inert gases extinguish fire by reducing the oxygen content of the atmosphere from an ambient 21 percent down to 12 to 15 percent, a level at which most combustibles will not burn. Inert gases are clean, electrically non-conductive, and characterized by low chemical reactivity, low toxicity, and low environmental impact. The inert gases have zero ozone depletion potential (ODP) and do not contribute significantly to climate change. The inert gases, however, cannot be compressed to liquids, and therefore must be stored as high-pressure gas, requiring the use of high-pressure steel distribution piping and a large number of high-pressure storage cylinders compared to other clean agents.
Figure 4. Aftermath of pre-action sprinkler activation on an in-cabinet fire
HFCs absorb heat to the point where combustion can no longer be sustained. HFCs are clean, electrically non-conductive, and characterized by low chemical reactivity, low toxicity, and low environmental impact. The HFCs have an ODP of zero, and their contribution to climate change is negligible: U.S. Environmental Protection Agency (EPA) analysis concludes that impact of emissions of HFCs from fire-suppression applications on climate change represents less than 0.01 percent of the impact of all greenhouse gas emissions, according to the EPA. HFCs are stored as liquefied compressed gases, requiring fewer cylinders and less storage space compared to inert gases, and standard piping can be employed.
Perfluoroketone FK-5-1-12, like the HFCs, extinguishes fire primarily by absorbing heat to the point where combustion can no longer be sustained. FK-5-1-12 is unique in that it is liquid at room temperature and is also characterized by high chemical reactivity, including metabolism in the human body when inhaled, according to a 2004 EM Novec technical brief.
Table 3 summarizes the qualitative between the clean agents. The table clearly shows that HFCs, provide the best overall combination of properties desired for protecting equipment and assets in mission critical facilities, followed by the inert gases. For these reasons, the most widely employed protection strategies for data centers involve FM-200 (HFC-227ea), the most prominent HFC technology, or one of the various inert gas technologies such as Inergen.
With downtime costs in modern IT facilities typically exceeding $50,000 per hour, it is critical to ensure that unplanned business interruptions are minimized. IT infrastructure fires do happen and can lead to extensive downtime and cost. Modern IT facilities are expensive, sensitive, and crucial to the function of business and society and the fire protection solutions these facilities must consider should protect both the electronic equipment within the facility and the greater value in use of the facility itself. Water-based methods such as sprinklers and water-mist systems are best suited to protecting structures. Protection of the sensitive, critical, and valuable data and equipment found within data centers requires a more comprehensive solution, which will protect these assets and also reduce or eliminate the costs of downtime and business interruption. Keeping critical facilities productive and running is best achieved using clean agent systems. Society’s increasing reliance on the global IT infrastructure increases the importance of providing clean, fast, and effective fire protection for these critical assets.