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 email@example.com is associate editor of BUILDINGS.