INDUSTRIAL APPLICATIONS

Nemoto Gas Sensors are used by instrument manufacturers to detect flammable or toxic gases wherever there is a possibility of gas escapes or build-up which may pose a danger to life or a risk to property.

There are few industrial environments where this is not so, but most of these risks are too small to warrant detection, or even giving them a seconds thought. There are some industries, however, where either the risk of a gas escape is significant, or the consequences of a gas explosion would be catastrophic - or sometimes both.

• Petrochemicals
• Water Industry
• Off-Shore Working
• Marine Environments
• Pharmaceuticals
• Chemical Works
• Food Industry
• Landfill Sites
• Gas Utilities
• Cabling Contractors
• Construction Sites
• Tall Office Buildings
• Research Laboratories
• Underground Car Parks
• Semiconductor Plants
• Refineries
• Mines
• Road/Rail Tunnels
• Hospitals
• Airports
• Foundries
• Power Stations
• Steel Works

RESIDENTIAL CO

NET residential CO sensors are designed to meet the increasing demand for low cost electrochemical sensors. Using a unique product design, NET sensors can be used to meet all the requirements of UL2034, BS7860, EN50291 and CSA16.9. All NET sensors include:

 

• 3 - Electrode design for greater stability
• Compact, Leak-proof enclosure
• Resistanct to shocks and vibration
• Terminals may be soldered
• Linear output
• Highly specific to target gas
• Unaffected by humidity
• Very low long term drift
• Low power consumption

The sale of residential CO detectors rose rapidly in the early 1990’s in the USA, predominantly due to the introduction of legislation. UL2034 was the first performance standard in the World and this allowed some US States to introduce laws mandating the installation of CO detection systems in all premises using gas as the primary heating fuel. Prior to 1990, some 2500 US citizens were killed each year by CO poisoning and many tens of thousands severely injured.

At that time, the primary technology was semiconductor and therefore all CO detectors were 110V operated. The consumer, however, demanded battery operated units and this resulted in the development of Biomimetic (blood cell) sensors. These devices simulated the production of COHb in the blood and required very little power to operate.

In the mid-1990’s a temperature inversion in the Chicago resulted in 2,000 false alarms in just one evening. It has been widely speculated that this was in the most part due to the original biomimetic sensors, where a small amount of CO was present in the atmosphere for a long period of time, activating the alarms. Subsequently, UL2034 was modified to include a 12-month 15ppm CO test.

More recently, companies using electrochemical sensors released CO detectors with LCD read-outs on them. This was a consumer driven development, whereby the consumer wanted real information about the amount of CO present in the atmosphere. As a result of this shift in customers’ expectations, there is a significant increase in demand for detectors with LCD read-outs. LCD requires an accurate CO sensor with an output that can be easily used to give a ppm reading. The sensor needs to be stable over long periods of time as well as being low-power and low-cost. For this reason electrochemical sensors are seen as the best way forward.

In the UK, the electrochemical sensor has always been the primary technology. This is a result of the requirements of BS7860 and also the UK consumers’ requirement for battery-operated units. In 2002 a new European Standard, EN50291, was introduced. This new standard has made it even more difficult for non-electrochemical technology to be used in Europe. The standard requires the sensor to discriminate between 30 and 50ppm CO between –10 and +50^oC. In addition, the sensor must be capable of withstanding 5000ppm and then being able to detect 30 and 50ppm CO after a short recovery period. This is almost unachievable using semiconductor and biomimetic technology and even a number of electrochemical sensors find this difficult.

FIRE DETECTION

NET Fire-CO sensors are designed to meet the increasing demand for low cost electrochemical sensors. Using a unique product design, NET sensors can be used to meet all the requirements of the current LPC and VDS performance standards.

The use of CO sensors to detect fires has been recognised for over 10-years, although the first commercial products were not widely available until the mid-1990’s. Electrochemical sensors have remained the technology of choice due to their unrivalled speed of response, long-term stability and extremely low power consumption.

Using CO sensors to detect fires offers a number of benefits over ionisation (radioactive) and optical techniques:

• smouldering fires produce little smoke but a lot of CO and a detector using a CO sensor can detect the fire up to 50 times faster

• modern fire doors prevent the escape of smoke but CO is able to escape quickly therefore a CO sensor can detect a fire much more quickly

• CO sensors are unaffected by dust and steam and therefore reduce false alarms

The main applications for this new approach are hotels, multi-occupancy buildings and those installations where false alarms are unacceptable, e.g. airports, factories, etc. In general, all installations of fire detection equipment will use a combination of different detector technologies, specifically located depending on the fire hazard.

There are two main approaches to developing a CO-based fire detector:

1.       CO-only – the main detection technology is a CO sensor, but this is combined with a thermistor that can detect fast burning fires that produce no CO. This is extremely popular in hotel installations where different detection technologies are installed in different parts of the building.

2.       Multi-Criteria – a CO sensor is used in conjunction with an optical or ionisation device. The key to this approach is to develop an accurate algorithm which compares the outputs of the various detection technologies to discriminate between “fire” and “non-fire” situations.

Where new fire detection systems are installed to protect life and to reduce false alarms, the use of CO sensors has grown significantly over the past few years and continues to do so. To support this growth, performance standards have been introduced. In the UK, the Loss Prevention Council (LPC) has produced a standard for the use of CO-only devices and BS5839 has been modified to include recommendations of where and when to install CO devices. In Europe, the VDS in Germany has introduced a CO standard and there is a current research project to develop a EN standard for multi-criteria devices.