The Development of Gas Detection Technology

The birth of gas detection can be dated back to 1815 with the birth of the Davy Lamp invented by Sir Humphry Davy. The Davy lamp was preceded by inventions by both William Reid Clanny and George Stephenson the latter conducted the first field tests at Killingworth Colliery a month before Davy presented his design to the Royal Society but was later deemed as a less safe solution than the Davy Lamp. The Lamp was a simple idea containing a wick with the flame enclosed by a mesh screen acting as a flame arrester the gasses could pass through but the mesh holes were too fine for the flames to propagate through. If the lamp was in the presence of explosive gasses the flame would burn higher with a blue tinge and if Oxygen levels were poor the flame would be extinguished. There were also indicators for the height of the flame which would indicate the levels of Carbon Dioxide if positioned at low levels in the mine.

The lamp was hailed as a success which would eliminate deaths from firedamp explosions within mines however it’s ultimate legacy was at best considered to be controversial as many deaths followed its original introduction. In 1835 a Select Committee on Accidents in Mines reported the introduction had led to an increase in accidents as mines or parts of mine previously closed off for safety concerns were being encouraged by the new technology. 102 men and boys were killed in a fire damp explosion in a Wallsend Colliery and many more fatalities were directly attributable to this working practice.

The other issue which had long been recognised as a killer of miners was Carbon Monoxide, being colourless and odourless this toxic gas was at that point not detectable by any means and thus came the miners canary.

The original idea of using canaries in coal mines is credited to John Scott Haldane “the father of Oxygen therapy”. His early research in the field of Carbon Monoxide led him to the use of birds as a species who were sensitive to the odourless Carbon Monoxide and other poisonous gasses toxic to humans. The idea was simple and effective if the animal became ill or died this would give miners a warning to evacuate. As canaries require vast quantities of Oxygen to let them fly and as they get a dose of Oxygen on both inhaling and exhaling they were a perfect transportable animal which could be carried by miners. From 1911 the canary was adopted by Miners in the UK, Canada and United States as an early warning for any potentially toxic hazards.

The widespread use of canaries was still in use in the UK until as late as 1986 when the humble canary was replaced by the “electronic nose” a digital reading monitor first reported by the BBC in January 1981. The “Electronic Nose” was pioneered by the coal boards mines rescue centre. The Mines and Quarries regulations section 24D -Fire and Rescue stated every manager was required to have some canaries at each mine ready and fit in the event of any incident.

For a number of years prior to the early trials of the “Electronic Nose” Infra-Red sensors had been used in the UNOR system which was based on the surface of the mine however the major problem with this system was the large delay times in response.

The surge forward for new technologies was once again brought about by a disaster. In 1926 a string of Oil Tanker explosions led the Standard Oil Company of California to sponsor research into a direct reading device for explosive gasses. Dr Oliver W. Johnson created the first catalytic explosive gas sensor based on the oxidation of gas on a platinum filament, a fundamental sensing technology still in use in modern day LEL gas monitors.

Meanwhile for many decades the unquantifiable canary method had become an industry standard in mines but it had been widely posited that a quantifiable method of calculating exposure particularly for Carbon Monoxide was essential as the small repeated exposures were having an unknown consequence on worker health. Spurred by the birth of the American Industrial Hygiene Association (AIHA) in 1939 and the first publication by Alice Hamilton “Exploring the Dangerous Trades” released in 1943 the first attempt to legislate for solvents to be classed as hazardous materials followed in 1944. This change in approach from immediate safety concerns to longer term occupational health meant the recognition of risk changed but as ever the access to affordable technology was still unable to catch up with the ambitions of practitioners.

In 1946 gas detection tubes came to market from two major centres in Europe and Asia covering at first Hydrogen Sulphide and then adding Oxygen and Carbon Monoxide specific measurement ranges. Gas detection tubes use a high density substrate contained within a tube with specific chemicals designed to react by discolouration to the presence of the target gas. These specific chemical reactions enabled the users to pull through a measured sample between 50cc-100cc and a simple colour change could be used to read off how much of the target gas were in the atmosphere. Within a few minutes a quantifiable level of gasses could be found. This gave Hygienists the first ability to measure small exposures and gauge them against potentially longer term health implications. Gas detection tubes now cover a vast array of gas types and are still in use for quantifiable data on gas levels where other technologies may be unavailable or less useful.

In 1953 the British Occupational Hygiene Society was formed as a charity with a view to reducing work related ill health and spread the word internationally regarding the latest developments and thinking in the scientific peer reviewed Annals of Occupational Hygiene.

In the early 1960’s the first Electochemical Oxygen sensors were developed allowing the incorporation of Oxygen levels into direct reading explosive gas monitors. This new technology based again on a chemical reaction enabled direct reading of Oxygen levels without the requirement for large or complex systems. During this same period Dr James Lovelock of University of Manchester was engaged by NASA to develop sensors to be used in the analysis of extra-terrestrial atmospheres and developed the first Photo Ionisation Detectors (PIDs) capable of monitoring a broad range of Volatile Organic Compounds (VOCs). This sensing technology using Ultra Violet light causes gasses with an Ionisation Potential below the output voltage of an Ultra Violet lamp to become ionised displacing an ion which can then be detected.

The US Occupational Safety and Health Act 1970 formed the Occupational Safety and Health Administration (OSHA) and American Conference of Governmental Industrial Hygienists (ACGIH) which lead to the first adoption of Time Limit Values for hazardous exposures in the US in 1971. Just 3 years later the Flixborough Chemical Plant Explosion in the UK killed 28 people and injured 36 and later that year the Health and Safety at Work Act 1974 came into UK law. This new act lead to the formation of the Health and Safety Commission and the Health and Safety Executive (HSE) in 1975. In 1976 in Seveso, Italy a small chemical plant suffered a catastrophic failure which resulted in the highest known exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This chemical release caused skin lesions in the local population this led to the European Union Sevesso Directive.

Over the following years of the 1980’s and 1990’s gas sensing technology was developed and refined to bring what had previously been large laboratory-based equipment or unwieldy application specific instrumentation into a more user-friendly form. Many companies developed this technology in several directions going from larger area gas monitoring and developing more general use portable and eventually personal gas monitors. With the introduction of digital technologies and printed circuit boards the analogue signals created by the direct reading sensing technologiesNIOSH could be displayed in new ways with interpretation of signal on digital screens so rather than focussing on an ever-moving pointer instantaneous signals could be displayed as meaningful readings.

Over this period several major industrial disasters occurred across the world including the Methyl Isocyanate leak in Bopal India which lead to over 16,000 deaths and the Piper Alpha disaster in 1988 where 187 workers on the platform died after a condensate pump failure. The countless examples of catastrophic safety failures promoted the largest leap forward in technology to prevent these disasters in the future. The goal of gas detection has always been to eliminate workplace or environmental fatalities caused by gas exposure or explosion and the continued development of technology covered later in this book will reduce these numbers further.

In 2005 EH40 came into force in the UK and covers similar limits to those recommended by OSHA and the US National Institute for Occupational Safety and Health (NIOSH) in the US for workplace exposures. This for the first time gave a comprehensive working document for chemical exposure limit thresholds for common known life limiting substance in use in every day working life.

Credits: Esther Inglis-Arkell – Gizmodo, BBC News– The Diminishing Role of Animals in British Coal Mines 1981, Robert Henderson – RAE Systems 2001


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