Data centers hold information that is absolutely crucial to the daily operation of large and small companies. Integrated fire safety and security systems are therefore vital for protecting data centers. Elaborates, Miguel Angel Coll, Head Fire Safety, Building Technologies Division, Siemens
All kinds of data – business, customer, employee and personal information – form the lifeblood of any commercial organization and therefore need to be protected against both external and internal threats. The volume of stored data is growing daily. This data has to be protected against increasingly more sophisticated internal and external attacks as well as theft and sabotage. However, while IT security generally offers good protection against external threats and internal vulnerabilities, fire safety is not always sufficiently covered. While the tendency to underestimate the threat of fire can be disastrous, fires are the most frequent and most catastrophic cause of damage for companies and customers.
High risk buildings
Data centers are subject to a much higher risk of fire than other commercial buildings. Electricity and the extensive cabling for IT systems are a constant source of potential ignition, particularly under raised floors. The many plastic components also contain a great deal of flammable material. Heavy power loads or a defective hardware part can rapidly lead to overheating or a short circuit.
Preventive and active fire safety measures are therefore essential in such sensitive environments. In ever more densely packed layouts, increasingly more powerful servers need equally powerful air-conditioning up to 8,600W/m2, resulting in higher air exchange rates. Some of the smoke produced by a fire is removed along with the air-conditioner’s air flow. This makes early detection even more difficult in conventional systems and increases the risk of the fire quickly spreading to other areas.
The smooth interaction between fire detection and extinguishing is the key requirement in implementing efficient fire safety and minimizing down times. Analyses by VdS, one of Germany’s leading independent testing institutions for fire safety and security, demonstrates that the interface between fire detection, alarming, control and extinguishing is the main cause of system failure. Early, reliable fire detection and the initiation of appropriate extinguishing measure are key factors in an efficient protection concept. It is therefore essential for the fire detection, evacuation and extinguishing systems to be compatible with each other.
Prevention beyond risk analysis
The role of risk analysis is extremely important in data centers. In addition to the early consulting activities to identify and plan for specific risks, it is also necessary to define future maintenance and modernization needs throughout the data center’s life cycle.
Along with preventing fire from breaking out in the server rooms, which lie at the heart of a data center, it is also important to consider the fact that the communication networks, battery room, power distribution equipment, power generators, cooling units and UPS hardware (uninterruptible power supply) also have specific fire safety requirements.
Early fire detection
Heavy power loads or defective components in a computer center can quickly lead to overheating or a short circuit. Fires in these environments usually begin slowly with a long period of overheating and smoldering before flames erupt. Smoke needs to be detected as early as possible to identify overheating and avoid an outbreak of fire. If smoke is diluted by a strong air flow, aspirating smoke detectors (ASD) provide the earliest possible warning even before people are able to discern the smoke.
The aspirating smoke detectors are installed directly in the circulating air flow and next to the server racks, allowing air samples to be taken continuously at danger spots. If smoke particles are detected, a pre-alarm or alarm is triggered, depending on the smoke concentration. The response characteristics are adapted to the particular application. Ranging from normal to high sensitivity, they make it possible to detect even the smallest smoke concentrations at an early stage. This saves valuable time needed to identify the causes of the fire and to take counter-measures.
Shutting down the equipment during the earliest phase of a fire outbreak is the safest way to prevent the spread of fire and corrosive smoke gases. This requires a combination of suitable hardware and software environments with a powerful early fire detection system. The power is cut off only after all the data has been transferred.
During a “gentle” shutdown, an intelligent server management system is activated when the fire is first detected and transfers the valuable data to adjacent data and server racks.
To prevent false alarms from activating the extinguishing system, two separate detectors must trigger an alarm before the extinguisher is activated. A single detector, on the other hand, will only trigger a pre-alarm.
In case of fire, standard alarm sounders or alarm sounders with sounder beacons are used to alert people in the building. For more detailed information and instructions, recommended is the voice alarm system with automatic voice messages and live announcements, which are automatically triggered by the fire detection system. All access points are closed after the data center and adjacent areas have been evacuated. The room is made airtight and the extinguishing agent can be released.
Different extinguishing methods
The method of releasing the extinguishing agent and selecting the best agent for a particular environment is extremely important in order to provide optimal protection. In critical applications, a dry extinguishing system is recommended, due to the sensitivity of the IT infrastructure. Two types of gas extinguishing systems are particularly good choices in data centers: systems with inert gases or those that use chemical extinguishing agents. Combined gas/ water extinguishing technologies are advisable in generator rooms at risk of thermal fires or fires with open flames.
The extinguishing agents depend on the application to be protected and on the room size. In smaller data centers with 200 to 300m2 of space, chemical agents such as Sinorix 1230 are the most economical option. In larger data centers with 300m2 of space or more, inert gases have proven to be successful. A system that combines nitrogen and water mist is the best option in the event of thermal risks, such as an emergency generator. The nitrogen smothers the fire, while the water mist cools the hot surface.
Although gas extinguishing systems are the best choice for protecting data centers, the latest studies show that, in very rare cases, hard drives can malfunction after the extinguishing system is activated. These problems range from automatic shutdown of the hard disk without damage after a restart to serious disturbances. These problems stem mainly from the relatively high noise level generated by a conventional gas extinguishing system when flooding the affected area. The silent discharge nozzle technology facilitates comparatively quiet yet effective extinguishing in data centers and server rooms.
Sinorix CDT (Constant Discharge Technology) is recommended for medium-sized to complex data centers. This inert gas system provides efficient extinguishing without pressure peaks.
Nitrogen is discharged into the extinguishing area under constant pressure during the flooding period. This even flooding makes it possible to design the piping network with smaller dimensions than in standard extinguishing systems and to also reduce the overpressure flaps by as much as 70%. It is therefore a particularly good choice for interior rooms, where large overpressure flaps are difficult to implement, due to structural features. Nitrogen is completely harmless for people, the environment and IT infrastructure.
In critical applications such as generator rooms, UPS systems maintain operation even in a power failure. Siemens recommends the Sinorix H20 Gas extinguishing system for equipment that easily overheats. This solution combines highly efficient nitrogen extinguishing technology with additional cooling water mist, reliably putting out fires and effectively preventing reigniting.
Expert planning, installation and commissioning are important to ensure the reliability of an extinguishing system.
For extinguishing with Novec systems, a minimum pressure of 10 bar ensures optimum evaporation and even distribution of the extinguishing agent in the room. This is an important factor, since Novec is stored in liquid form, while extinguishing takes place in the gaseous phase. It is therefore advisable for even the most remote nozzles – that is, the nozzles with the lowest pressure – to use a minimum nozzle pressure of 10 bar. This ensures that the extinguishing concentration is reached quickly and the fire is extinguished as fast as possible. A minimum nozzle pressure of 10 bar is also recommended for extinguishing with inert gases. This leads to an ideal mixture between the extinguishing agent and the ambient air, thus putting out the fire quickly and reliably.
If a room is more than five meters high, installing a second nozzle system is recommended. Doing this distributes the extinguishing agent quickly and evenly, so that the necessary extinguishing concentration can build uniformly everywhere. In chemical extinguishing systems, a flooding time of ten seconds ensures that the extinguishing concentration builds quickly and the fire is extinguished efficiently.
In the event of an open fire, the rapid buildup of the extinguishing concentration helps minimize the development of harmful hydrofluoric ac i d , a produc t of chemical decomposition. Openings have to be designed so that they close automatically by the time flooding begins. Openings also must be reduced to an unavoidable minimum. If possible, ventilation systems have to be turned off before flooding begins or at the same time. If this is not possible, compensating for the loss of extinguishing agent must be calculated.