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January 31, 2014 -
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A properly designed and selected fire detection and notification system is an essential component of an overall data center protection strategy. Aspects to consider when evaluating fire detection options include early initiation and response, as well as the interface with other systems such as suppression, ventilation shutdown, and early operator warning.
In today's data centers, power densities may exceed 400 watts per square foot, almost all of which is transformed to sensible heat by the servers, storage devices, and networking equipment located within the data center usable raised floor area (white space). Such power densities require significant quantities of air (3,700 cfm or greater) to provide cooling at typical design conditions. Fire detection and suppression systems designs need to account for the challenges posed by high airflow velocities associated with high power densities.
There are numerous detection approaches available for use within data centers to provide early warning of a fire. The inherent criticality and essential nature of the equipment in data centers will often dictate the detection approach. Detection strategies typically include spot-type smoke detectors, air-aspirating smoke detectors (e.g., smoke sampling chamber with a sampling tube network), or a combination thereof. As with any approach, there are advantages and disadvantages to these strategies. The data center design and stakeholder goals help to guide the detection design.
Spot-type smoke detectors are a very common smoke detection strategy used in data centers. Newer types of intelligent, spot-type detection technologies use built-in algorithms with multiple sensors or multi-criteria to adapt to their environment and minimize the likelihood of false alarms. These detectors often rely upon multiple analog sensors — such as smoke, heat, and carbon monoxide sensing elements — that are processed through proprietary algorithms.
Cross-zoned smoke detection is typically the preferred strategy when utilizing spot-type detectors in data centers. This design relies upon the activation of two alarms before subsequent action, such as opening of a pre-action valve or clean agent discharge. A cross-zoned strategy minimizes the potential for an unwarranted discharge of a fire suppression system. The initial detector can provide a warning to operators and staff within the data center. The need for two separate detectors to activate, however, results in activation delay. This delay may compromise property protection and business continuity goals.
Air-aspirating or air-sampling detection is becoming increasingly popular in data center applications. This type of detection is known for its ability to detect a fire in its incipient stages and therefore provide earlier warning and faster response time than traditional detection.