Clean agent fire extinguishing systems have applications for Class A and Class B fires, but also can be effective in suppressing Class D combustible metal fires. They can use either manufactured or inert gasses, and disrupt the heat production of a fire, absorbing enough heat from the flames to put them out. In this video, fire protection expert Lee Kaiser explains the different types of clean agent systems and considerations in choosing the correct system for your space.
Lee: "There's two buckets of clean agents. There are the manufactured agents, so these are gases that are made in a factory somewhere. They're chemical gases, and the other type are inert gases, so the manufactured agents that we use are FM-200. A lot of people just know their system as an FM-200. They don't even know it's a clean agent system, so FM-200 is a brand name for a certain type of gas out there. ECARO or FE-25 system sold by Fike here in the U.S. NOVEC 1230 a gas made by the 3M Company. A number of manufacturers sell it.
Manufactured Vs. Inert
These gases, the manufactured agents, work to extinguish flames primarily by heat absorption, so as they discharge into a space, they have a given heat capacity to absorb heat from the flame. They make the flame chemistry unstable and it basically goes out, so that's how those systems work. They discharge in a fast period - ten seconds to discharge all the agent into the space. Now, inert gas systems are a different type, these are gases that are extracted from the air that we're breathing right now. There's Inergen sold by Ansul, Argonite and ProInert two gases, IG-55 a 50% blend of argon and nitrogen: Argonite sold by Kidde Fire Systems, Pro-Inert sold by Fike Corporation. And then some of the manufacturers have nitrogen systems, so nitrogen and another gas, Argon.
Clean Agent Systems and Different Classes of Fires
This is one place where we're going to sidebar and talk about Class D fires, so combustible metals fires. There are few options for putting out those types of fires, but some of the manufacturers that I know of, Kidde and Fike, they're working in the lab to extinguish Class D fires using 75% concentrations of argon. They're having some success, quite a lot of success, putting those fires out. I think Fike has produced a system for dust collectors that collect Class D fire dusts with argon systems at 75% concentration, so that's one of the things that's happening out there. When you have other rooms, you know, we couldn't use a 75% concentration of argon by itself. That would be like a CO2 system, and lower the oxygen too much It does work to extinguish those Class D fires.
Otherwise, for normal fires, Class B, Class A fires, inert gas systems work through heat absorption like the chemical clean agents do and also lowering the oxygen concentration. That's the inert piece of their name, lowering the oxygen concentration down to around 14% and remember that we're, you know, at 12% we need to be really exiting the room quickly. They have longer discharge periods between 60 and 120 seconds to lower the peak pressure that's experienced in that room, so we don't have structural issues when the system discharges.
Considerations for CLean Agent Systems
Some practical considerations between manufactured systems and inert gas systems. Manufactured systems typically have a smaller installed footprint, so there's less tanks, less equipment, it takes up less floor space and, you know, we value that a lot here in the U.S. In fact, the United States use probably more manufactured gases and inerts. Europe, things are different, you know, they use a lot more inert gas agents. Lower discharge pressures for manufactured gases. Lower first cost, so that's also important here in the U.S. It takes less capital to install a system in the first place, but more expensive recharges because I have to pay to put the juice back in the bottles, after it discharges.
Now, inert gases, a couple points for them, longer attention times. They're able to hold within the space. Clean agents are one category that's not highly tolerant of unclosable openings, so we do something called a door fan test to measure how long will the agent be retained in the space after discharge, so a system just typically not very tolerant of unclosable openings. No fogging during discharge for inert gas systems. Higher first costs because we're paying for more cylinders and nozzles, but the benefit is an even higher level of environmental responsibility, when we're installing an inert gas system and less expensive recharges. Some of the manufacturers of these systems will actually give you an environmental guarantee that if you discharge your system, they'll give you free gas back and all you have to pay for is the label to change out the bottles."