In addition to the matters covered earlier, data centers raise special considerations for fire protection, including issues involving containment strategies and commissioning.
With larger deployments at power densities higher than an 8 kW/cabinet, conventional hot-aisle/cold-aisle approach is insufficient. Air tends to leak from the supply to the return side and vice-versa, bypassing the IT equipment altogether. In such cases, a physical barrier is employed to prevent such short cycling. This strategy is called either hot- or cold-aisle containment, depending on which airstream is isolated. The fire protection systems design must be carefully reviewed when containment is employed, particularly when retrofitting existing facilities, as the separation can affect detection function, sprinkler coverage, and alternative suppression systems design. In-rack detection and suppression provides an innovative solution and allows for early detection and suppression. Some AHJs insist that sprinkler protection be provided within the contained area while others accept partitions that fall away in case of a fire.
Detailed commissioning of data center protection systems is important to confirm that the systems perform as intended. A common test for data centers is a so-called room validation test which loads the data hall with resistive load banks to simulate the full power draw of the space. A word of caution: Under full load, areas within the white space can get quite hot, with local temperatures exceeding 150 degrees F. Care must be taken during full load tests so that thermal sensors interfaced with the fire alarm system and sprinkler release mechanisms do not activate a false alarm and ultimately actuate the suppression systems during a non-fire event.
For some time, NFPA 70, The National Electrical Code, article 645, required an emergency power off (EPO) feature, which allowed complete power-down of the data center in emergency situations. This is typically implemented as a covered push button located near the principal entrance or exits to the data hall. In some cases the fire alarm system was interfaced to actuate the EPO sequence. This practice was criticized because of the potential for accidental activation. In fact, some operators would place the system permanently in the "test" position to prevent such mishaps. With the 2011 version of NFPA 70, this requirement has been relaxed, placing discretion over the need for an EPO with the AHJ.
There are a wide variety of approaches to addressing issues of capacity, resiliency, cost, and schedule in data centers. Careful design that accounts for the range of possible fire scenarios allows the fire detection and suppression systems to meet reliability and business continuity goals and objectives. Commissioning is important, as designs can work well on paper but need to be properly implemented to meet the protection goals.
Jeffrey Tubbs, PE, FSFPE, is a principal with Arup where he leads the Boston Consulting Practice. He has nearly 20 years of experience in fire and life safety design and code consulting, with significant experience in critical infrastructure and multidisciplinary projects. He can be reached at jeff.tubbs@arup.com.
Garr Di Salvo, PE, LEED AP, leads the critical facilities business for Arup in the Americas. He has been involved in data center design, construction, and operation for more than 15 years and can be reached at garr.disalvo@arup.com.
Andrew Neviackas, PE, is a fire engineer in Arup's Boston office. He has more than 6 years of experience in fire protection engineering design and code consulting, including numerous projects involving data centers and their associated critical equipment. He can be reached at andrew.neviackas@arup.com.
A Comprehensive Approach To Data Center Fire Safety
Evaluating Fire Detection Options For Data Centers
Data Center Fire Suppression Systems: What Facility Managers Should Consider
Data Center Fire Protection: Containment and Commissioning
