Concerned that sensitive equipment may be water damaged if your fire sprinklers are activated?
Traditional sprinklers are great at preserving your building structure from a fire, but they’re not designed to protect assets within your space. Whether you have a telecommunications closet, transformer room, flammable liquids, a computer lab, or data center, chances are your operations could take a serious hit if these valuables become wet.
Enter special hazard fire protection systems, commonly referred to as waterless sprinklers or clean agent systems. These sprinklers use inert gases or liquid chemicals to smother flames. By avoiding a rush of water during a fire, damage to interiors and critical infrastructure is minimized.
Gases and Chemicals
Special hazard fire protection systems that are considered replacements for halon either use a halocarbon compound (compounds containing carbon, hydrogen, bromine, fluorine, iodine, and chlorine) or an inert gas such as argon or nitrogen, says Chris Jelenewicz, an engineering program manager with the Society of Fire Protection Engineers.
“The inert gas system works by displacing oxygen, while chemical agents absorb combustion heat,” adds Al Thornton, global manager for DuPont Fire Extinguishers.
Early detection is key with these systems. Whereas traditional sprinklers incorporate fire detection into the sprinkler itself, clean agent systems rely on separate detectors to trigger them from a control panel, Jelenewicz notes.
When activated, gas is discharged in 10 seconds or less with chemical agents. Inert gas systems can take upwards of two minutes, Thornton explains. Because the smoke detectors sense a fire in its earlier stages, the elapsed time between detector initiation and gas discharge is far quicker than conventional sprinklers.
“We had a case where a patient was in an MRI machine undergoing testing when the circuit card caught fire. The system activated within seconds – before the technicians could run to the room. The fire was put out and the patient, aside from a good scare, was otherwise fine,” recounts Thornton. “The hospital merely had to replace the faulty card, as opposed to the entire MRI, and it was back into the revenue stream in no time.”
Applications and Space Considerations
Special hazard sprinklers are best used in well sealed or protected environments where you can control gas levels.
“Large areas such as a warehouse or open office where the gas volume is difficult to concentrate, or a space like a dock or lobby where gas can disperse easily, are not suitable applications,” says Rocco Lugrine, head fire and life safety expert with Kinetix Fire & Life Safety Experts.
One of the advantages of these sprinklers is that they can easily be used in renovation projects, notes Lugrine, such as when a space is converted to a server room, computer lab, or kitchen.
“However, these areas need to be correctly designed for the pressure differential that will occur if inert gas sprinklers are triggered. Otherwise, you could blow out the walls or ceiling,” notes Larry Grodsky, senior product manager for fire products at Siemens Industry, Inc. “It’s safer to use positive pressure dampers to direct room air out of the space.”
The size of your coverage needs and alloted space may also dictate whether you use inert gases or chemical agents.
Unlike water sprinklers, which measure coverage per square foot, clean agent systems are based on cubic volume.
“This is three-dimensional protection for vertical spaces,” says Thornton.
Inert gases aren’t condensable and require a high volume for discharge. Depending on the size of the space you are protecting, you may not have the room to store all of the cylinders needed.
Chemical agents are typically used at 6-10% by volume of the protected space, and can be condensed and stored as liquids, Thornton explains. You can use one cylinder of chemicals as opposed to 10 cylinders of inert gas for the same coverage.
Testing and Maintenance
Like traditional sprinklers, waterless systems require annual maintenance and testing to ensure that they’re ready to go at a moment’s notice, says Lugrine.
These systems are inspected twice a year – a visual check on all devices and weighing cylinders to confirm that agent levels haven’t dropped.
The good news is that agents have an indefinite shelf life, so cylinders don’t have to be drawn down or have a hydrostatic test while in service, notes Thornton.
One potential breakdown of the system is between the detection system and system activation, stresses Jelenewicz.
“You also want to look for the same problems as you would with traditional sprinklers – obstructions, tampering, and layout changes,” Grodsky recommends.
Because these systems are less common and have more moving parts, costs are higher than traditional sprinklers.
“$3-5 per cubic foot is a baseline for these types of systems,” says Thornton. “Regular sprinklers average $3 to $4 per square foot.”
As with any life safety system, you have to justify an investment on this scale based on risk mitigation.
“It will be your worst day when you need this type of system,” says Grodsky, “but you don’t want any doubts that your assets will be protected.”
Jennie Morton firstname.lastname@example.org is associate editor of BUILDINGS.