Designing Datacentre Fire Suppression Systems

Datacentres and server rooms are in a constant state of evolution when it comes to the top three concerns of IT technology, critical power and critical cooling. As servers become more powerful, they need more power to support larger facilities and cloud based services. This in turn leads not only to the need for more power but a greater risk of fire and related damage.

In terms of datacentre or server room fire protection systems have also evolved to keep pace with the demands of the environment and how to protect larger and more power-hungry server environments. However, the core principles of a sound fire protection strategy remain the same; to warn early, provide safe evacuation, reduce further damage and ultimately extinguish the fire hazard.

Datacentre Facility Fire Suppression Strategy

Any large server room or datacentre will have several areas where a fire or smoke risk can arise. A fire can break out within the boundaries of the datacentre facility and indirectly threaten it or there could be a fire within the facility itself, within the data hall or a secondary support area.

Wherever the risk of fire or smoke damage arises, a proven fire suppression strategy will seek to extinguish the threat as fast as possible. This means using the most advanced air sampling smoke detectors to provide early warning through a fire/alarm panel and monitoring system, sprinkler systems, double-knock zones and the right fire suppression agent.

Risk Assessments and Business Continuity

One of the most useful documents when generating a fire suppression strategy is a Risk Assessment and Method Statement (RAMS). One key aspect to also link to this exercise is that of business continuity. When a fire occurs, and is extinguished the damage to the local facility and servers can be extensive. Evidence always points to an 80% business closure rate where fires are experienced to critical systems and information where a sound business continuity plan has not been executed. For server room facilities and datacentres this can be include disaster recovery suits, cloud data storage and mirror facilities.

Learning Environment

The datacentre industry does not have an open book policy when it comes to learning from datacentre or server room fire incidents. This is partly down to the signing of non-disclosure agreements (NDAs) by suppliers and clients as an incident can damage a reputation. For a colocation datacentre that provides a safe and secure physical environment for client servers, a fire suppression system discharge incident can damage overall confidence and the saleability of the service to other clients.

Virtualisation and Fire Ignition Sources

Many server rooms and datacentres now use virtualised server configurations. Whilst virtualisation reduces the number of hardware server platforms required, (multiple servers run in a virtual environment) the power demands of the hardware have risen. When placed in a server cabinet, virtual servers can lead to power draws of 15-30kW or more. Not only does this mean more power and cooling requirements for the server cabinet but also the risk of fire and the speed with which it can spread if not quickly identified, isolated and extinguished. It can also be argued that colocation datacentre facilities may have a greater fire risk than enterprise sites, where clients can install their own server hardware.

Server hardware itself contain combustible and flammable materials, in terms of the plastic cases, PCBs and components such as AC and DC capacitors fitted to server mother boards and other devices including uninterruptible power supplies. UPS batteries can also suffer unexpected failures and through thermal-runaway pose a fire risk.

Smoke Detection

Of course, rapid smoke detection is the primary stage for any fire suppression system. Once an alarm is trigged, if the source is quickly extinguished this can not only prevent fire damage but also accidents and potential personal injury.

The principle fuel for any fire is air or to be more precise the oxygen within the surrounding environment. From this perspective, the fire suppression strategy should consider air flow and movement within the facility and this means working with HVAC designers and engineers. The HVAC company should be able to provide a thermal map and model of air flow within the data hall and surrounding areas to ensure that smoke detectors can be installed at the right monitoring points. To trigger the smoke detectors the smoke density must also be sufficiently high, even for sensitive devices and this level is generally higher than most people can detect normally.

Once detected, fire trained officers should be the ones who investigate and if necessary tackle the initial cause of the smoke alarm if a main evacuation signal is not trigged. If the latter occurs, the fire has already taken hold and more than likely the suppression agent has been released into the environment. If not, thermal cameras can be used to identify potential heat and smoke sources. Known as ‘hot spots’ these heat sources can develop within UPS systems, servers, PDUs, sub-distribution boards, plant room transformers, bus bars, LV switchboards. Where possible, equipment giving rise to the smoke may be isolated and shutdown or tackled by a trained fire officer with the appropriate fire extinguisher.

Room Design, Raised Access Floors and Ceiling Voids

Raised floors provide a plenum through which to route power and data cables as well as cool air. For fire fighters raised floor voids and the room above suspended ceilings can pose greater hazards when fighting a fire. Firstly, smoke (and fire) could build up in these areas before alarms are triggered. In addition, they may have a forced air supply that can fuel fire spread and speed.

Raised access floors and suspended ceilings are commonly used in datacentres and server rooms. Where they are used, the fire suppression strategy must allow for these and provide adequate smoke detection, sprinklers and the right choice of extinguishing agents. Floor tiles and ceiling tiles must be capable of easy access and entry if ant potential fire is to be identified and suppressed quickly.

Emergency Power Off and Post Fire Detection Impact

An emergency power off (EPO) button may be installed close to the main exit door so that power is ‘killed’ to the equipment in the server room vicinity including the UPS system. In the case of an uninterruptible power supply, an EPO can be connected to an input on the UPS system itself which causes it to power down and turn off instantly the EPO is pressed. The same EPO facility can be used to power down HVAC equipment and close vents into the room.

EPO can also be automated and controlled on release of the fire suppression agent. A double knock system is common whereby two zones have two trigger smoke alarm detection before the extinguishing agent is released. Even then there may be a fall-back position to cancel this and delay the EPO if it is felt that the fire risk is localised and contained enough. Whether this is allowed is dependent upon legislation and guidelines.

There is no doubt that the risk of fire is increasing within datacentres and serve room as the power demands rise. Whilst the principles of fire suppression remain the same, advancements are being made in monitoring and detection systems as well as fire extinguishing systems and agents.