Beam detectors are used for detecting smoke. Recent updates to this technology have resulted in the Open Space Imaging Detector (OSID) manufactured by Xtralis. This style of detector is perfect for applications in environments like atriums, freezers, aircraft hangars, cold storage warehouses, shipping warehouses, enclosed parking facilities, sporting arenas, stadiums, concert halls, barns, and tunnels.
The OSID by Xtralis uses two different wavelengths of light, infrared and ultraviolet, to create a more nuanced detection system that can give you an idea of what is obstructing the beam. It can differentiate between a spider crawling across the detector, a plume of dust, a solid obstruction and, most importantly, smoke because each of these things produce different types of disturbance to the wavelengths.
In this live demonstration, fire protection expert Lee Kaiser gives a practical demonstration of the Xtralis OSID beam detector. Below is a summary of the video
Functions and Features of Beam Detectors
Lee: "This white device and its companion over there is a beam detector. It's called the OSID - Open Space Imaging Detector. It's manufactured by Xtralis, a company now owned by Honeywell. We know Xtralis because they make VESDA. VESDA is air sampling smoke detection. We're going to get to that in a little bit, but first we're going to talk about their beam detector. We feel that the technology in this detector is worth you knowing about. If you ever have a beam detection application, you really should consider using this detector because of some of its unique attributes which makes it better than other beam detectors.
The OSID uses two wavelengths of light. Most beam detectors use just infrared light. This uses both infrared and ultraviolet light. Also, it has a wide field of view for a 3‑D approach. This device, called The Imager, is actually a camera. Cameras have a focal point and they have a field of view, so this detector can be tolerant of building movement because it can expect that that's going to move a little bit over time, and it can deal with it because it's a camera and not just a point sensor.
So what’s the advantage of using both ultraviolet and infrared light? Smoke is a fairly fine particulate and as it breaks through the beams it affects the two wavelengths of light dissimilarly. Smoke doesn't reduce the infrared light as much as it reduces the ultraviolet light, so when the detector sees a dissimilar reduction in those two light sources as it receives it, it knows that it's smoke. Dust tends to be larger particles of particulate so when it breaks through the beams, it reduces both light beams equally. This detector, unlike other beam detectors, has some level of dust discrimination, to understand whether it is dust or is it smoke. Now with obstructions, the beam's lightning is cut out completely. I'll show you how that works when there's a fixed obstruction that gets in the way of making the detector operate.
The Imager can also receive multiple beams of light from different emitters. You can have an array of emitters set up to have a number of beams across. Those beams are discrete inputs into this detector, so it knows which beam is being obstructed via smoke, and you can do this cross-zoning type of thing to release a suppression system, to have confirmation that we've got detection on two different areas. We had a large pharmaceutical warehouse where we released a pre-action sprinkler system using this type of technique.
The Imager in Action
Let's try some tests with this. So I've brought up is a piece of software that I have running on my laptop, and I'm tied into the detector with a USB cable. This is normally how we'd set a system up. So we can see where the system normal, and it's looking at Emitter No. 1 there, and then we see fire, trouble and okay over on the left-hand side. So a green light, green lights are good in fire-suppression systems or fire alarm systems. So this system is normal and ready to go. So we're going to do some demonstrations.
Detectors in Action
I need a volunteer. Who's ready to be my first victim? Okay, come on up. Come on up. What's your name?"
Lee: "Everybody give Tim a hand for being bold. Can you show me both hands?What I observed was that your hands are not very hairy which means you'll work for this demonstration. We're going to simulate a spider crawling across the detector as an obstruction. That will help us understand how the detector works, but if your hands are too hairy, you'd be like a tarantula and freak everybody out. So you're going to go over to that detector and spread your hands out and wave it in front of the detector.
Next, you're going to simulate an obstruction by using this piece of paper. This is where it takes a little physical stamina. You seem like a robust man, so I think you'll be fine. Hold this up in front of that. It'll take about 30 seconds or so, and then it'll go into trouble condition and we'll observe that. When you remove it, then it'll come out of trouble condition.
Now, we could activate that with smoke, but we have other detectors to set off in the room, so we're not going to do that. We're going to use this listed testing gel to simulate smoke, so you're going to hold that up there, and after a couple seconds, it'll go into alarm and we'll see the fire activation go up there. So spider, obstruction, smoke, I'll talk you through it. So go ahead over there and stand next to that detector.
Before you get started, let's show everybody your picture. Do you see that green, can you kind of see yourself? Dan, would you stand up? We can see Dan right there. It's not a live image, it's just a static image to help set up the detector, but you get an idea that that's really a camera there.
The next thing we're going to bring up is a little graph of what's happening with the detector. On this graph, this is a live image, of what's happening with the ultraviolet light, which is the blue line, and the infrared light, the red line, as it comes in. So there's little variations, probably just due to dust in the air, whatever's happening here. Now I need my spider. Spread your fingers out and wave back and forth, and we're going to start to see how that changes. We'll start to see these climb. This graph is actually an inverse, so you start to see it climbing there, see that it's live and working and there are active reductions in the light transmittance that's coming to the imager from the emitter.
Now let's simulate an obstruction. So what we're going to see here is both light sources reduced to zero. Go ahead and hold that up there, and all of a sudden this will spike and change the scale on my graph and we'll adjust from there. Remember this inverse, both the red line and the blue line go to 100 percent, which is 100 percent reduction in the transmittance, so hold your hand up there and we'll move this over so we can see the trouble light come on when that happens. Keep it up.
Okay, in a second we'll get a trouble. We've got the trouble, so we've got the yellow light there but on this indicator light here, this will flash yellow. We know that that device is in an off-normal condition or a fault condition. You can take your hand down, and it'll show the automatic restoration of trouble back to normal operations. It dropped and it'll restore. See how the light transmission went back to normal? You see that automatic restoration, automatic clearing, to normal condition. Any time we've got a fire alarm system, when we have a device that goes in default and it's fixed, it automatically returns the panel to normal, same with this device.
Now we're going to simulate smoke. You're going to hold that up there and we're going to watch the dissimilar reduction in the light transmittance. On the screen here, we can see that we've completely reduced the amount of ultraviolet light, the blue line just went to the top, but we've only slightly reduced the infrared light coming in. The red line just went up a little bit but not all the way taken down, so that's how it dissimilarly sees that. It's also the fire notification is flashing. We see the red LED flashing over there, so we know that that's the device that's causing the alarm, and it also says it on the screen.
Fires are latching conditions. We need to reset this detector or reset it via the panel before it will come out, so we're just going to let that flash.
Tolerance to Building Movement
I'm going to try to show here is the tolerance to building movement. This device is a laser alignment tool. This is what we use to set up and align the detector at first. You guys should be able to see the red laser. We're going to install it in the detector so we can see where it's pointing. It's closer to there, and now we're going to twist the stand to start to see some building movement. What we're going to see is this is going to begin to climb over here on the graph. Click scroll again, so we can see that better. Let's move it a little bit more. We're reducing the amount of light that's going into the detector, but we haven't gone into trouble. Maybe that's one one and a half degrees of building movement. Let's move about the same, let's say that's two or three degrees of building movement. It'll climb a little bit more.
I'm not a structural engineer, but I'd expect that any building that has that much building movement - three degrees of movement on the steel frame - we've got some permanent structural damage. That's probably our concern at that point and not our fire detector going into trouble condition, but let's move it a little bit more to see how tolerant it really is. Let's say that's maybe five degrees total building movement there. We can move it so much we will go into fire condition. We've got structural issues at this point, and who cares about my detector if it's in trouble or not.
So why would we use the OSID detector?
- It has better performance over traditional beam detectors – better false alarm immunity and dust discrimination.
- No misalignment problems. It eliminates false alarms due to building movements and misaligned detectors.
- High reliability. So there are beam detectors out there that have motors installed to track building movements, but this doesn't have to do that. Less moving parts keep it simple. It’s just a good detector.
Any time you have a beam detection application, you should consider the OSID. We've had a lot of success with it, and it works great as a beam detector."