The Five Ss: A Guide to Selecting Effective Data Center Fire Suppression

The modern data center may not always be a single, large space and may instead be a series of data halls. The heat generated by the servers in these halls poses a fire risk, so protection methods should be selected accordingly. Good fire system design can help data centers protect people, equipment, uptime and business continuity in the event of a fire.

There are several firefighting options suited to data centers:

• Sprinkler systems

• Water mist systems

• Halocarbon gas extinguishing systems

• Inert gas extinguishing systems

However, there is no one-size-fits-all solution. Five critical factors (safety, space, speed, spend and sustainability), referred to as the "Five Ss", can help prioritize protection objectives and guide system design. Considering these Five Ss can help determine the best firefighting solution for each data center.

1. Safety

In most data centers, protecting occupants and maintaining system uptime are typically the highest priorities. Therefore, a key protection objective is to extinguish a fire and prevent its spread using an agent that's safe for people and equipment.

Gas systems using halocarbons and inert gases are designed primarily to extinguish a fire. This discharge of a gas extinguishing system, especially in a non-fire condition, will not adversely affect people or equipment.

Water-based systems, such as sprinkler systems and water mist systems, are engineered to control or suppress a fire.  The discharge of a water-based system will not harm people (other than getting them wet) but may damage equipment.

In addition to these systems, aerosols have also been used for firefighting in data centers. If aerosols discharge, the particles may be inhaled by occupants, so these systems should not be used in occupied areas. Aerosols also leave a fine residue that can damage equipment and require extensive cleanup. European Standard EN 50600-2-5 advises that aerosols should not be used in occupied spaces or in spaces containing electronic equipment.

Overall, a gaseous system backed by a water-based system provides an optimal level of protection without undue risk of damage to equipment or the safety of people.

2. Space

Modern data centers typically have a room allocated specifically for fire protection system equipment. The space required for this equipment depends on how much room is available and the type of fire protection equipment required in the region where the data center is located. Some regions — including North America — mandate a sprinkler system for building protection. In that case, if the space is already allocated, other protection objectives may call for the addition of a gas system.

Gaseous systems usually require less space than water sprinkler or water mist systems. Gaseous systems use gases stored under pressure within containers, providing a comparatively large firefighting capability in a relatively small footprint. Sprinklers and water mist systems typically require pumps and a water tank, which may have a larger footprint than gas containers.

3. Speed

To prevent a fire from spreading, it's critical to contain and extinguish it in its earliest stages. Gas systems make it possible to contain and extinguish a fire within minutes of first detecting smoke.

Gas systems are connected to an early warning fire detection system designed to sense smoke in the very early stages. After more than one detector senses smoke, the sequence to deploy the system begins. After a short time delay, usually not more than 30 seconds, the gaseous system begins to discharge. Halocarbon systems discharge entirely within 10 seconds for rapid extinguishment, while inert gas systems for data centers take about two minutes to discharge fully. During the discharge period, the agent impacts the fire until it's extinguished.

With water-based systems, the discharge is dependent on heat. Heat can take time to accumulate during a fire event, especially if there is high air movement in the space, like that from mission-critical HVAC equipment. Depending on the device's location, considerable time may pass before there is sufficient heat to activate the sprinkler head or water mist head. However, pre-action sprinklers connected to a detection system could detect smoke and prime the sprinkler system. 

It should be considered that air movements within the protected space can also affect smoke's ability to reach the smoke detector, so it is important to ensure the fire detection system's design accounts for the airflows present.

Gas systems have a faster response compared to water-based systems and can detect fires in incipient stages, making a gas system backed by a water-based system ideal.

4. Spend

In a perfect world, every data center would have an early warning detection system and a gaseous system backed by a water-based system. However, budgets need to be respected, and system design governed by budget starts with what is mandated by code. In North America, for instance, building code requires a sprinkler system.

While the size and complexity of the data center will dictate the upfront cost of a firefighting system, there are additional considerations. Hazard geometry and the cost of cleanup and downtime after system discharge can also impact the total cost of ownership.

Understanding hazard geometry, including factors such as air movement, can help predict system efficacy during a fire event. For instance, air handling equipment is critical to data center performance and uptime and cannot be shut down. If a gas system discharges while air handling equipment is running, it will not hinder system performance and may even help by drawing agent into affected equipment. In comparison, the high airflows of air-handling equipment can detrimentally affect the performance of a water-based system by moving water away from the fire. The design of the water-based system should recognize the airflow rates and determine whether it can be deployed within the system's approved limits.

The costs of cleanup, downtime and equipment replacement must also be considered. It is very likely that the cost of cleanup and downtime will be significantly higher with a water-based system than with a gas system backed by a water-based system. Gas systems use clean agents that produce no residue. In the event of discharge, a gas system requires post-discharge ventilation, resulting in minimal cleanup. Downtime is limited to equipment damaged by fire. In the event of a water-based system discharge, affected spaces require cleanup, while equipment damaged by water and/or fire typically requires replacement. There is some downtime until both are complete.

5. Sustainability

Sustainable operation is a high priority for data centers, and environmental impact extends to fire protection. For a water-based system, consumption may be a consideration in water-insecure areas. For these regions, a gas system may be preferred.

There are no environmental concerns for inert gas agents, such as those offered in the Johnson Controls IGS-300 system. And while there may be environmental concerns about halocarbon agents, FK-5-1-12, which is offered in the Johnson Controls SAPPHIRE system, is a fluoroketone with a negligible global warming potential and is exempt from use restrictions arising from concerns about climate change.

Designing ideal fire protection for each data center

Every data center is unique, and its fire protection solutions should align with its needs and core protection objectives. To streamline the selection process, partner with a provider that offers flexible, fully compliant solutions and proven performance. They can help you leverage the Five Ss to prioritize objectives and design the ideal fire protection solution.