Alternative benefits of hybrid systems

Alternative benefits of hybrid systems

For centuries, building owners have relied on traditional fire sprinklers and their supporting systems for the protection of the structure, and its occupants, as well as a wide range of materials and flammable contents. Fire sprinklers continue to protect property and save countless lives each year throughout the world and are recognised for their longstanding performance capabilities and long-term reliability.

These systems have certainly earned their place in both new construction as well as renovations and real estate re-purposing projects where the hazard classifications can vary significantly. However, while fire sprinkler systems can control many fire scenarios, they also often result in unwanted ancillary damage from the resultant water discharge. In this article, LEN SWANTEK, Victaulic’s Director of Global Regulatory Compliance, explores the alternative benefits afforded by hybrid fire extinguishing systems.

The history of hybrid fire extinguishing technology dates back more than ten years and originated as a pioneering idea to combine two previously distinct systems into one: water mist and an inert gas, typically nitrogen. The hybrid fire extinguishing system uses nitrogen gas and water released through an emitter to produce very fine water droplets (typically around 10 microns in diameter) as compared with that of a standard sprinkler (1000+ microns) or standard water mist nozzle (100+ microns).

The water droplets are so small that they remain buoyant within the inert gas as a kind of ‘micro fog’, which allows these droplets to fill a volumetric space more uniformly and absorb heat more effectively, without the need to maintain room integrity or provide additional room venting.

This combined use of water and inert gas has a cumulative effect and not only controls or suppresses a fire but has the capability to fully extinguish fire by reducing the heat as the water droplets flash to steam and displacing oxygen via the use of nitrogen. The small 10-micron water droplet size of hybrid systems provides an exponentially larger relative total surface area available for the rapid cooling of fire as compared to traditional water mist droplets or fire sprinkler water droplets. The nitrogen gas also allows the hybrid system to extinguish fires that are not in direct line with the system’s nozzles in a total flooding-type application.

Due to these unique properties, hybrid fire extinguishing systems are used to protect a wide range of hazards. They are commonly specified in the protection of high-hazard applications such as industrial machinery spaces including power generation plants, turbine enclosures, automotive manufacturing, steel production, as well as flammable and combustible liquids storage, steel mill pickling lines, recycling facilities and mining installations.

These types of high-hazard applications require a fire protection system that not only releases quickly in the event of a fire but also minimises the impact on property and equipment from fire and water damage, allowing the business to minimise downtime and continue operating.

While hybrid fire extinguishing systems can be used in virtually any commercial or industrial application, these systems have been specifically designed to minimise water usage making them ideal for the protection of sensitive and irreplaceable materials such as libraries, museums, information technology data centres, server rooms, data storage and large archive facilities. The fine droplets and minimal use of water combined with the inerting properties of nitrogen afford an advantage for hybrid extinguishing systems in these highly sensitive applications.

The development of hybrid fire extinguishing systems was quickly recognised by global leading fire protection organisations as being distinct from other competing fire suppression technologies, thereby requiring the creation of new governing codes and standards.

Initially drafted in 2009 and first published in 2012, FM Approvals, LLC created the first hybrid system approval standard, FM 5580 – Approval Standard for hybrid (Water and Inert Gas) Fire Extinguishing Systems. Nearing 200 total pages, this standard contains dozens of technical requirements, including system performance testing for corrosion resistance, leakage, discharge characteristics, cylinder and water tank requirements, operational and actuation testing, as well as at least eight dedicated sections for different full-scale fire test scenarios.

The fire scenarios include 1 and 2 MW shielded spray fires using both diesel and heptane fuels, which simulate the protection of machinery spaces and turbine enclosures. And, for data centre applications, there are fire test protocols that simulate cable tray fires in raised subfloors. In all tested fire scenarios, the hybrid system extinguishes the fire completely.

Several years later in 2014, the National Fire Protection Association’s Standards Council voted to approve the establishment of a new NFPA committee to begin drafting a new NFPA installation standard for hybrid fire extinguishing systems. This was largely driven by the fact that two related NFPA installation standards did not fully cover and apply to the unique features of a hybrid system. NFPA 750 – Standard on Water Mist Fire Protection Systems could not be referenced for hybrid systems since inert gas is a defining feature of the system not included within the scope.

Similarly, NFPA 2001 – Standard on Clean Agent Extinguishing Systems could not be used for hybrid systems since water is used as an extinguishing media, again not covered within the scope of this standard. As a result of NFPA’s efforts and their dedicated, world-class technical experts, NFPA 770 – Standard on Hybrid (Inert Gas and Water) Fire- Extinguishing Systems was first published in 2021.

This installation standard has been quickly adopted by the fire protection industry and has been incorporated by direct reference in 13 NFPA Standards, 3 NFPA Codes and 2 Codes under the jurisdiction of the International Code Council (The International Building Code and The International Fire Code).

There are 20 additional NFPA Standards that are currently in the revision cycle which are reviewing proposals and comments to add language to recognise hybrid fire extinguishing systems.

Many of these standards that are in the revision cycle, have already accepted the hybrid technology and are awaiting their official release. There are over 25 additional NFPA Standards that will receive proposals to recognise hybrid systems when they are in their revision cycle.

The NFPA 770 technical committee continues its work today and is currently drafting the 2026 edition, which will include a number of new service applications.

Hybrid fire extinguishing systems have multiple benefits compared to other fire protection systems. Unlike other suppression technologies that use chemicals or other agents, hybrid systems are clean. By using water and nitrogen, there is no environmental impact and no negative effect on human health from discharging these clean agents.

In fact, at least one hybrid extinguishing system is recognised by the US Environmental Protection Agency’s Significant New Alternative Program (SNAP) as an acceptable total flooding fire suppression substitute, having zero global warming potential and zero ozone depletion potential.

Additionally, the hybrid system is designed to fully extinguish a fire whereas other types of systems typically are designed for the purpose of only suppressing or controlling the spread of a fire. Hybrid systems optimise the use of water, typically using only gallons of water during a full discharge during a fire event.

This means the water and nitrogen can easily dissipate after the fire is extinguished with very little clean up required afterwards, thereby minimising any impact on property or otherwise sensitive equipment.

Hybrid fire extinguishing systems play a vital role in almost any application where both the risk of fire spread and water damage are of significant concern. The functional characteristics of these systems are recognised by specification engineers, facility owners, insurance underwriters, local fire authorities (AHJs) and fire equipment certification bodies.

Through rigorous testing and qualification by such agencies as UL LLC and FM Approvals, these systems have demonstrated their extensive capability in controlling and extinguishing fires in complex applications. Displacing oxygen in shielded fires is one of the most beneficial characteristics as compared with traditional water mist systems.

Left unaddressed, shielded fires can spread inconspicuously resulting in further damage and presenting unexpected safety risks for the responding firefighters. As technology and fire hazards evolve over time, advances in fire suppression technology must also keep pace and rise to the challenge of protecting highly hazardous and sensitive materials and occupancies, while minimising the impact on the environment and business operations. Hybrid fire extinguishing systems have been specifically developed, tested, and proven to meet these growing challenges while providing unique advantages over competing fire suppression technologies.

As such, these systems will continue to be specified and installed in a growing number of industries and applications as they stand ready to provide their fire extinguishing capabilities and advantages in virtually any fire scenario.