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GSS LEDs used in fire protection application

Data logger can create a 3D map of the carbon dioxide levels in an enclosed space

Most CO2 sensors work by measuring how much light is absorbed by CO2 molecules in the 4.2 to 4.4 microns range, known as Non-Dispersive Infra Red (NDIR) absorption. The amount of absorption indicates how much CO2 is present.

Scotland-based GSS has developed a range of proprietary LEDs specifically tuned to emit at these wavelengths. The LEDs use very little power and turn on almost instantly, enabling sensor readings to be made in a few seconds. As a result, GSS has pioneered the development of CO2 sensors that can be powered by batteries for long periods of up to ten years.

One of the most interesting applications for this technology is in monitoring cylinders of CO2 used for fire protection of switch rooms or control panels, and other confined space environments which house electrical components, computer or process equipment such as server farms.

Now using GSS technology, a company called CO2Meter has developed a data logger, the CM-0003, that is capable of measuring up to 100 percent CO2 concentrations. The portable device is suited for leak detection testing in fire extinguisher systems, and can detect even a slight change in the level of CO2. By attaching a length of tubing, the unit can be run in real-time along pipe connections and valves to pinpoint leaks - even in hard-to-reach places.

This unit is also used to create a 3D map of the CO2 levels in a particular space, by sampling from both horizontal and vertical locations. This helps determine when it is safe for emergency services to enter an area after a CO2 extinguisher has been used.

"Our original design used a GSS ExplorIR-W CO2 sensor, as the low power requirements of their LED-based technology enabled us to create a portable, battery-powered product that could go weeks between recharges," explained Irene Hicks, COO of CO2Meter. "It is also highly accurate right up to 100 percent CO2 concentrations, which is vital for a sensor in safety applications. However, an almost instant CO2 reading is needed in some situations, so in future we will be using a high speed GSS SprintIR-6S sensor in our datalogger. This sensor takes 20 readings per second, so it's ideal for recording fluctuating CO2 levels, particularly in fast changing environments. The beauty of the SprintIR-6S is that it's still low power enough to be used in our portable data logger, so you can have high speed and low power sensing effectively combined."

Carbon dioxide is an ideal fire suppressor for many applications, because apart from actual fire damage, there is no clean-up or residue associated with a CO2 system - unlike with foaming agents or water. When a fire starts, high-pressure CO2 is released into the area it is protecting. Carbon dioxide gas displaces the oxygen until there is no longer enough required for combustion. The fire can then be controlled or extinguished.

However, there are two key challenges when using CO2. First, the cylinders of CO2 used in these Fire Suppression Systems could leak. Therefore, the areas where they are stored need to be monitored. Second, when such a system has been deployed, the atmosphere must be checked to ensure that the CO2 has dispersed to safe levels for re-entry.

A customer of the CM-0003, who uses them for full discharge tests of CO2 fire suppression systems, said: "The meters are small enough to take as carry-on luggage, which I find very useful. I typically use three or four meters simultaneously, with test times ranging from 30 to 60 minutes each. To date, I've used these CM-0003 meters for testing well over 200 sites."

Rachael Yates, marketing manager at GSS, added: "We have a very close working relationship with CO2Meter who use a variety of our sensors in their products. The solid-state design of our LED-based sensors makes them particularly rugged so that they can withstand the rough handling that portable devices are subjected to. We are delighted to be working with them as they integrate our latest designs of ultra-fast reacting sensors into their product range. In particular, our unique, low power, 100 percent CO2 sensors are opening new market opportunities for them to create solutions for."

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