Considerations for Gaseous Suppression Systems in Data Centres
Advisory Note
March, 2010
Gaseous fire suppression systems are commonly used in data centres and other similar mission critical applications. The primary reason for their use is that compared to traditional systems such as fire sprinklers, the potential for non-fire damage to equipment or materials is significantly reduced. Furthermore post fire cleanup can generally occur much more quickly where a gaseous suppression system is present and has operated to extinguish a fire resulting in reduced total business interruption times.
In the past, options for gaseous suppression were generally limited to Carbon Dioxide or Halon based systems. Halon has been banned internationally for general use and Carbon Dioxide is toxically lethal and thus not ideal for use in modern data centres.
Today there is a range of alternative systems available which are suitable for use in data centre and computer room applications. When specifying a gaseous suppression system there are a number of factors that must be considered.
AGENT TYPE: One of the first things that must be considered is the type of extinguishing agent to be used. Broadly speaking there are 2 categories of extinguishing agents, inert gasses and chemical agents.
Both categories provide some cooling due to release of compressed gas, however the dominant mechanism of extinguishment for each is different. Inert Gasses 'suffocate' the fire by displacing air in the enclosure, while chemical agents interrupt the chain reactions in the flame. As part of their extinguishing mechanism chemical agents 'break down' when exposed to heat and flames. This results in production of 'by-products' which may be corrosive and/or toxic. However, these systems are normally designed for rapid discharge (<10s) suppressing the fire quickly and minimising volume of any by products. In contrast inert gas system by definition do not breakdown into by-products. However they usually have significantly longer discharge times (60-90s) to achieve extinguishing concentration, during which time the fire is producing products of combustion.
SPATIAL REQUIREMENTS: Due to the higher volume of gas required, inert gas systems require larger space for storage cylinders than for chemical agents. Inert gasses typically displace 30-50% of the protected enclosure volume, whereas chemical agents are typically less than 10%.
AUTOMATIC SMOKE / FIRE DETECTION: The type of smoke or fire detection that will initiate the system needs to be considered in relation to how computer room operations staff will respond to events in the computer room.
STORAGE CONTAINER LOCATION: Due to the requirement for rapid discharge the storage container location for chemical agents is critical and cannot be
located too far away from the protected enclosure. Inert gas systems are generally more flexible in relation to location of agent storage containers.
ENCLOSURE ROOM INTEGRITY : All total flooding gaseous suppression systems require the protected enclosure to be relatively well sealed in order for the system to maintain the design concentration for a minimum specified period (typically 10 min). This can sometimes be problematic, particularly in existing rooms.
AIR HANDLING: It needs to be considered whether the air handling system will continue to run during and after gas discharge as this will affect the gas hold time characteristics.
ENCLOSURE VOLUME CHANGES: All gas systems have some sensitivity to changes in room volume due to installation of new equipment. Inert gas systems are usually more sensitive to room volume changes due to the fine tolerance between extinguishing concentration and maintaining an atmosphere which can support life.
ENVIRONMENTAL CONSIDERATIONS: There are two key criteria in relation to the environmental impact of the suppression agents, Ozone Depletion Potential (ODP) and Global Warning Potential (GWP). Due to international regulation via the Montreal Protocol, all gas suppression agents for general use (such as in a computer room) must have an ODP of zero.
Inert gas systems typically have a GWP of 1 or less (1 being the equivalent of carbon dioxide). Traditionally chemical agents have a high GWP (typically in the range of 1,000 – 10,000), however a recently a chemical agent has been developed with a GWP of 1.
ON SITE RESERVE CYLINDERS: The need for a reserve cylinder bank needs to be considered in relation to the criticality of the protected enclosure. Once a system operates it is offline and the room un-protected until such time as the storage containers can either be re-filled or replaced. Typically refilling of containers must be undertaken off site, so there will typically be a delay of at 1 – 5 days while the cylinders are taken off site, refilled, returned to site and re-installed.
Each of these issues needs to be considered carefully when selecting the optimal type and configuration of gaseous suppression system for a particular application.
For further information, please contact
Geoff Flower – Engineering Services Manager
on 03 9279 7100 or
While every effort has been made to ensure the accuracy of the information in this publication A. G. Coombs assumes no responsibility for errors or omissions or for any consequences of reliance on this publication.