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Special Flames
In a fire event, each flammable material emits radiation with a special spectral pattern according to the combustion by products created in the process. In addition to the typical hydrocarbon flammables that have a similar spectral pattern with the CO2 and H2O peaks, other highly flammable and toxic substances have unique spectral patterns according to their main emitting species.
A list of flammable gases/liquids with special spectral patterns that require special flame detectors are listed herein:
Hydrogen
Hydrogen (H2) the lightest gas is used extensively in various industrial processes as a chemical reducer (in oxidation reactions) and as a hypergolic fuel (reacting with oxygen) for space rocket engines.
In a hydrogen fire, the main intermediate is the hydroxyl radical OH that further reacts with oxygen to produce the main combustion product, water vapor H2O. The energy from this combustion process is emitted in UV, Visible and IR at specific spectral bands.
H2O emits mainly in the near IR band with a strong peak at 2.7 micron. Detecting the emitted IR radiation from a Hydrogen flame enables fast and reliable optical detection with high immunity to false alarms. Detection distance was somewhat limited before using UV/IR detectors but the SharpEye Models 40/40M Multi IR and the 20/20SH Triple IR will both detect a 20" (0.5m) 'invisible' Hydrogen flame at 100 ft (30m).
Hydrogen containing gases like Ammonia (NH3), Hydrazine (N2H4), various chemicals containing hydrogen like Metal Hydrides (AlH3), Acids (H2SO4), Hydrogen Sulfide (H2S), etc., exhibit similar emission spectra in combustion processes, hence their flames are detected reliably and fast by the SharpEye UV/IR Flame Detectors which can pick up the H2O and OH radiation at UV and IR. Simultaneous presence of both IR and UV signals allow these detectors to monitor for these fire from these hazardous materials
Ammonia
Ammonia (NH3) is a highly flammable, colorless toxic gas, extremely irritant with a pungent odor. SharpEye UV and UV/IR Detectors are suitable for detection of ammonia flames, which are almost invisible, with high UV and near IR (2.7micron) radiation peaks.
The SharpEye UV flame detectors (20/20U-UB and 40/40U-UB) as well as the UV/IR flame detectors (20/20L-LB and 40/40L-LB) are suitable for ammonia flames detection.
Alcohols: Ethanol, Methanol, IPA, MTBE and other gasoline oxygenates
Methyl Tertiary Butyl Ether (MTBE), a key component of clean-burning gasoline, ethanol, methanol and other gasoline oxygenates that are used in various parts of the world as gasoline additives and to some extent substitutes, pose a unique fire detection problem as their flames are almost invisible!
These flames produce mainly H2O as a combustion product, which emits radiation in the near IR 2.7 micron spectral band. SharpEye UV/IR Flame Detectors employ this IR channel coupled with the UV spectral channel to identify the radiation emitted by the OH intermediate combustion product.
Click on the specific detector below to find out the sensitivity to alcohol flames: 40/40M, 40/40I 20/20L-LB, 40/40L-LB, 40/40U-UB
LPG/LNG
The SharpEye Triple IR (IR3) Flame Detector is specially calibrated to detect LPG fires and LNG fires in LPG/LNG terminals, storage tanks, loading and off-loading areas.
The latest 40/40I and 40/40M detectors offer a significant increase in the methane and propane detection area covered by just one detector
LNG - Liquefied Natural Gas is composed primarily of methane and as such has a unique spectral pattern in the UV and IR spectral bands. SharpEye 20/20U-UB, 20/20L-LB as well as the new series 40/40U-UB, 40/40L-LB, 40/40I and 40/40M are suitable for detecting these flames.
LPG - Liquefied Petroleum Gas is composed of various light hydrocarbons that have a wide range of emission bands in both the UV and IR spectra thus enabling the use of several detectors depending on the required detection sensitivity and range. Click for detailed info on the various applicable detectors: 20/20L-LB, 40/40L-LB, 40/40I and 40/40M.
Click here for link to the full application note
Propellants & Explosives
Spectrex had developed a unique, high reliability, fast response flame detector as part of an Air Force project to address its ammunition production and handling safety needs.
The most important requirements issued by the armed forces were fast response time (<5 milliseconds) and high immunity to false alarms. Spectrex Inc designed the Model 20/20F which had been tested by the US Air Force Laboratories and was found to meet the requirements.
| Material Description | Time to Detection |
| RS41 Incendiary Composition | 2-5 msec. |
| M206 IR Flare Composition | 3-4 msec. |
| M14 Propellant | 12-41 msec. |
Silane
Silane (SiH4) is an extremely flammable and toxic gas. The substance may spontaneously ignite on contact with air.
Detecting Silane fires by conventional IR or UV/IR optical flame detectors (which rely on the 4.3 micron peak of CO2) is difficult, since Silane's combustion products emit almost invisible radiation (similar to hydrogen flames).
Silane combustion products, OH and H2O, are responsible for most of the Silane flame emission in the UV (below 0.3 microns) and near IR (2.7 microns) spectral bands.
SharpEye models 40/40L or 20/20L (and LB versions) and the ultra-fast UV/IR SharpEye 20/20F are most suited - the ultra-fast UV/IR detector in particular for detection of a Silane-air explosion, providing alarm within several milliseconds, well before it develops into an uncontrollable situation.