Canadian Consulting Engineer

Fire Protection: Mission Critical – Protecting Data Centres

The communication and instantaneous access of information has become part of our daily life and depends on a global network of interconnected information and telecommunication systems and data centres.

August 1, 2012   By Cel Chow, P.Eng., Gage-Babcock & Associates

The communication and instantaneous access of information has become part of our daily life and depends on a global network of interconnected information and telecommunication systems and data centres.

Meanwhile, information and communications technology equipment and its ancillaries have changed drastically in the last 20 years and represent more complex fire safety challenges. Their higher fire loads come with their compact electronic components, fair amount of electrical cables, higher energy use, and cooling airflow environment. These challenges in data centres affect the design of traditional fire safety systems. For example, high airflows may dilute the smoke concentration and may disperse the fire suppression agent.

The National Building Code of Canada, NFPA 75, “Protection of Information Technology Equipment,” and NFPA 76, “Fire Protection of Telecommunications Facilities” outline the design and construction requirements of buildings hosting data centres, and the fire safety requirements in these data facilities. The requirements in these codes and standards, however, may not fully satisfy the data centre’s need to provide continuous service to its clients and users. An objective-based design approach to the fire protection systems might help to meet those stakeholder demands.

Based on the functions and importance of data centres to the stakeholders, data centres can be classified in three categories:

Level 1 – for non-essential or useful IT equipment, where its loss due to fire would result in only temporary inconvenience and minor expenses. Loss of equipment can be quickly restored without serious consequences.

Level 2 – for important IT equipment, where its loss would cause a significant delay in the resumption of operations, or where the value of the IT equipment is significant.

Level 3 – for essential or irreaplaceable IT equipment, where its loss would cause a critical delay in resuming operations. The loss of services can be vital to life safety, such as air traffic or transit control systems, or 911 call centres.

Initial fire protection design criteria can be developed by issuing safety instructions to staff and by limiting the quantity of combustible materials in the data centre.

Following are criteria related to an actual fire event.

Provide early warning notification. It is essential to discover a fire at its earliest stage (incipient), while the size and intensity of the fire is small. Given the nature of human behaviour, building occupants and emergency responders must be made aware of the fire emergency by means of an early warning notification.

Hence, the provision of effective smoke detection is critical. A conventional smoke detection system, which consists of a listed fire alarm control panel with photo-electric or ionization type smoke detectors, primarily addresses the detection of fire and smoke for life safety of the occupants. However, it does not provide additional protection to the essential equipment.

From the protection of asset and operation continuity point of view, an aspirating type early smoke detection system may be employed to actively sample the high airflow environment. An aspirating smoke detection system consists of a fan unit and a group of sampling tubes distributed in the room. The system actively draws the air in the room to the smoke sensing unit and can detect a fire at its incipient stage. For more effective smoke detection, sampling tubes are often installed in the path of the airflow and even inside the equipment cabinets.

Provide first defence. Once the centre operators or building occupants are notified, it is assumed that they will take appropriate action, such as by attacking the incipient fire using a Class B (CO2 or clean agent) portable fire extinguisher. This will create an opportunity to limit the severity of the fire and heat and smoke damage to the sensitive electronic equipment within the area.

Provide total flooding fire suppression for the equipment and data. If the first defence is unsuccessful, the fire’s heat and smoke will activate the total flooding fire suppression system. These total flooding systems can minimize the damage to the equipment in the centre and the building. They are generally clean agent systems such as Inergen, FM200 and NOVEC 1230 (trade names).

The Inergen gas agent contains 52% nitrogen, 40% argon and 8% carbon dioxide. The gases are retrieved from the atmosphere with zero greenhouse gas emissions, therefore this system is the most environmentally friendly. Fire suppression is achieved by reducing the oxygen content of the atmosphere from 21% to the 12%-15% range, which would not support combustion for most ordinary combustibles.

The FM200 agent contains hydrofluorocarbons HFC-227ea. This agent extinguishes fire predominantly via heat absorption. FM200 is characterized by its zero ozone depletion potential and minimal impact on climate change.

Another commonly used clean agent for fire suppression is NOVEC-1230, which contains perfluorinated ketones (FK-5-1-12). It is characterized by its low toxicity, zero ozone depletion potential and minimal impact on climate change. Both FM200 and NOVEC-1230 can be stored as liquefied compressed gases, requiring fewer cylinders and less storage space for the agent.

Provide water based fire protection of the building. If a data centre is located in a building which is required to be sprinklered by the local building code, the sprinkler system is required to be installed in accordance with NFPA 13, “Standard for the Installation of Sprinkler Systems.” Instead of standard wet sprinkler systems, pre-action sprinkler systems are generally provided in the essential equipment rooms to prevent water damaging the equipment from the sprinkler operaing prematurely or due to a failure in the sprinkler piping.

Provide passive fire compartments against fire spread. Rooms equipped with essential equipment or hosting critical operations, such as control rooms and data storage rooms, are often separated from the remainder of the building by a 2-hour fire separation. This limits the spread of a fire from other parts of the building and also minimizes the heat and smoke damage, allowing the essential equipment to continue to operate.

Provide redundancy in building systems to maintain undisrupted operations. In order to limit the effects of a fire, system redundancy should be considered to minimize the possibility of operation down-time. Dual power supply to the data centre equipment and ancillary systems should be provided through two different power distribution systems in the building. The electrical cables should be fire-rated cables or protected in fire-rated shafts when they pass through a high fire hazard area. The air-handling and conditioning systems for rooms with essential equipment or data storage should be totally separate from other air handling systems in the building.

With a review of the classification and operation objectives of the data centre, fire protection design criteria can be developed accordingly through the fire risk and hazard analysis. cce

Cel Chow, P.Eng. is a principal of Gage-Babcock & Associates, engineering consultants for fire protection, life safety and security, in Vancouver. www.gbacan.com, e-mail c_chow@gbacan.com


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