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Data Center HVAC Practices Can Pose Challenges to Fire Detection
July 10, 2013 -
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Today's tip discusses some of the ways data center HVAC practices can cause challenges to detecting a fire as quickly as possible.
Current fire codes do not have a sufficient understanding and provisions in place for many data center environments, according to David Quirk, a principal engineer with Verizon Wireless. Quirk recently presented at the NFPA conference in Chicago on the subject of fire detection performance in data center environments, specifically as they are impacted by airflow.
In data centers, there is a lot of air turbulence. CRAC units working to cool the space in addition to the many fans on servers and air pushing up out of raised floors all create airflow patterns unique to data centers. The increased air velocity and increased airflow pose a challenge to fire detection because they make it harder for enough fire byproducts to reach a smoke sensor quickly. An of course, especially in a data center, the goal is to identify a fire as quickly as possible.
In addition, unlike a general assembly space or even a typical office, there are lots of obstructions and unusual fuel sources, like data cards and wires. Many data centers operate at temperatures and/or with air velocities that exceed the parameters of existing code, which can leave operators and AHJs a little bit at a loss as to what is best practice for installing detection systems.
Some particular challenges are posed by data center operations strategies that are otherwise beneficial. For example, hot/cold aisle configurations direct airflow in such away that a smoke detector centered above the cold aisle could inadvertently be placed in a spot with little air movement, which could slow detection.
Another example of a good energy strategy that could impact fire detection is using airside economization. Being able to operate on just fresh outdoor air is great for saving energy on conditioning the air, but brining in fresh air and exhausting it out cuts down on how much air is recirculated in the space, which means it can take longer for a detector to sense smoke in the space. In addition, the usage of filters on HVAC units can have the unintended effect of scrubbing smoke particles out of recirculated air, potentially increasing detection times.
With a goal of providing the fire protection community with better data on how fire detection systems actually operate in high airflow environments like data centers, Quirk says NFPA is currently working on a variety of studies to provide data for consideration during the next code cycle.