High Airﬂows, High Risks: Protecting Datacenters
Aspirating sensor technology offers a high level of protection for datacenters while addressing the unique conditions and complications of these environments.
Although there is a low probability of fire in datacenters, even a small fire in a single piece of electronic equipment can result in extensive dam-age and costly interruption of IT operations and services. That’s why these unique building spaces represent an in-demand customer segment for installing fire systems contractors.
Unplanned downtime can be directly linked to lost revenues. The Aberdeen Group estimates the average loss at $138,000 per hour (Source: Datacenter Downtime: How Much Does It Really Cost? March 2012). Indirect costs – such as lost employee productivity, the cost of time to recreate lost work, damage to a firm’s reputation or brand, and losing customers – are more difficult to quantify but still significant.
Therefore, the very early warning detection provided by aspiration systems is critical for identifying small fire events like precursor smoldering or overheating equipment. Let’s take a look at requirements and strategies pertaining to integrated datacenter solutions, above ceilings and below floors, and at ceiling level.
Integrated Detection and Suppression
Datacenter fire protection strategies often integrate numerous facets into one solution, such as a combination of suppression and smoke detection systems. “Datacenters require comprehensive coordination. This is not necessarily limited to sprinkler and fire alarm, but also includes electrical, mechanical and architectural components,” says Andrew Neviackas, PE, Arup senior fire protection engineer and code consultant.
When suppression systems are in-stalled as part of a datacenter’s fire protection strategy, there is a need to identify and investigate an alert or alarm condition prior to an extinguishing suppression system operation. Depending on the suppression system(s) used, there could be a need for a fire detection system interface to initiate sprinkler pre-action valve operations or damper-closing operations prior to clean agent release, or to shut down HVAC systems and other equipment.
Air sampling detection plays an important role in these operations by providing alerts and alarms at appropriately set smoke detection levels. If there is a threatening fire in development, the typical Fire 1 and Fire 2 alarm setting can be programmed to initiate pre-action valve or clean agent release. Where a sprinkler or water mist system is supplemented by a clean agent system, it may be necessary to control suppression/extinguishing system operations with two alarm levels of an air sampling detector (e.g. Fire Alarm 1 and Fire Alarm 2) or to use two independent detection systems.
For example, an aspirating detector may control the sprinkler pre-action valve while a second detection system triggers a clean agent release after an appropriate time delay (e.g. 30 seconds). Aspirating detection systems provide the early response needed to initiate an extinguishing system in the event of a developing fire. Quick water application and system effectiveness is typically improved by early operations during the fire event. Air sampling systems assure prompt extinguishing system action.
When depowering is necessary (shutting down HVAC systems and equipment that’s a potential ignition source), it can be accomplished with either manual or automatic disconnect features. Aspirating smoke detection can also be valuable to the sequence of depowering operations. Premature shutdown of HVAC systems can cause an immediate temperature spike in the facility, resulting in electronics equipment damage. Early staff response initiated by an aspirating smoke detection system’s alert and action settings can confirm the need for any associated air handling shutdown.
In the event of an actual fire, the typical Fire 1 and Fire 2 alarm settings can be programmed to initiate pre-action valve release (or clean agent release) and HVAC shutdown and equipment depowering. The depowering of equipment assures better clean agent suppression and less chance of equipment damage.
Air Distribution Challenges
Understanding the air distribution approach of datacenters helps identify the key airflow paths, as well as areas where airflow is minimal and unlikely to carry smoke particulate to a sampling port location. Datacenter air distribution usually involves one or more of three basic approaches: flooded, targeted and contained.
The flooded approach uses a supply and return air distribution system in which the only constraints to the airflow are physical boundaries of the room or space, such as the walls, ceiling and floor. Due to the extent of hot and cool air mixing, aspiration air sampling points are recommended at the ceiling and at the HVAC/CRAC (computer room air conditioning) unit air returns and supply-side outlet grills.
The targeted approach also uses a sup-ply and return air distribution system. The difference, however, is that the supply or return is placed near or adjacent to the IT equipment through the use of ducts, perforated tiles, or even a piece of localized equipment within the IT racks to direct the airflow to/from the IT equipment.
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