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Aflare, also sometimes called afusée,fusee, orbengala,[1][2]bengalo[3] in several European countries, is a type ofpyrotechnic that produces a bright light or intense heat without anexplosion. Flares are used for distress signaling, illumination, or defensivecountermeasures in civilian and military applications. Flares may be ground pyrotechnics, projectile pyrotechnics, or parachute-suspended to provide maximum illumination time over a large area. Projectile pyrotechnics may be dropped from aircraft, fired from rocket orartillery, or deployed byflare guns or handheld percussive tubes.
The earliest recorded use of gunpowder for signaling purposes was the 'signal bomb' used by the ChineseSong Dynasty (960–1279) as the Mongol-ledYuan Dynasty (1271–1368) besiegedYangzhou in 1276.[4] These soft-shelled bombs, timed to explode in midair, were used to send messages to a detachment of troops far in the distance. Another mention of the signal bomb appears in a text dating from 1293 requesting their collection from those still stored inZhejiang.[4] A signal gun appears in Korea by 1600. TheWu I Thu Phu Thung Chih orIllustrated Military Encyclopedia, written in 1791, depicts a signal gun in an illustration.[5]
In the civilian world, flares are commonly used as signals, and may be ignited on the ground, fired as an aerial signal from apistol-likeflare gun, or launched from a self-contained tube. Flares are commonly found in marinesurvival kits.
Distress rockets (aka "rocket-propelled parachute flares"[6]) have been mentioned in the modern era for civilian maritime emergencies since at least 1856. TheU.S. Nautical Magazine of that year mentions the use of "rocket stations" for ship related emergencies.[7] White rockets were solely used until 1873, when commanderJohn Yorke of theRoyal Navy suggested that rockets for distress should have a distinctive color. The request was made to help ease confusion between ships in distress and rockets used bypilot ships.[8] By 1875, theBoard of Trade (UK) had issued regulations for Captains in regards to night signals. Rockets containing at least 16oz ofcomposition were only to be used as a sign for a ship in distress. Passenger ships at the time were required to carry 12 of these rockets.[9] TheMerchant Shipping Act of 1894 further stated that these rockets were to be fired one at a time in short intervals of approximately one minute apart.[10] Distress rockets continued to be used in different colors, as was the case withRMSTitanic. At the time shipping companies had "a particular kind of distress rocket (that differed by color)". Each ship was also given a guide of colors to use depending on what signal was to be sent.[10][11]
Modern red distress signals are mentioned by theUnited States Bureau of Mines as early as 1959, where they state "12 handheld rocket-propelled parachute red flare distress signals" are to be used by ocean going ships.[12] The color red was eventually incorporated for use in the United States on 17 December 1979 as part of a "Universal color language".[6] Red distress rockets and/or flares are now internationally recognized symbols that indicate a ship in distress.[13][14] TheInternational Convention for the Safety of Life at Sea (SOLAS) has standards for visual signals, including both handheld and aerial flares. Handheld flares must burn for at least one minute at an averageluminosity of 15,000candelas, while aerial flares must burn for at least 40 seconds with a 30,000-candela average luminosity.[15]
While rockets and flares are still an option for signaling distress, they have since been surpassed by improved technology. Distress signals can now be sent using automated radio signals from asearch and rescue transponder. Other internationally recognized methods include the radio messageSOS, which was used during the 1912sinking of theTitanic, and the emergency procedure word "Mayday", which dates to the 1920s.[13][16][17]
Another type of flare is thefusee, which burns with a bright red light.[18] These come in two main types which are used for roadways andrail transportation. The first type are fusees used for roadways which are known ashighway flares orroad flares.[19][20] These are commonly used to indicate obstacles or advise caution on roadways at night and are found in roadside emergency kits.[21] Law enforcement also may use these flares (either propped on a biped or laid flat) to signal traffic hazards or that a road is blocked, often as a more visible replacement for traffic cones.[22][23][24] Law enforcement in the United States usually usemagnesium-based flares that last from 15–30 minutes.[24]
Fusees used for rail are known asrailroad flares, they are commonly used to perform hand signals or used as torches inrail transport applications.[18][25] Railroad flares can burn for at least 10 minutes, are not fastened to train cars, and are handheld by railroad personnel for protection at night.[18] It was argued during an Appeals case that railroad flares are much more visible thanlanterns.[18] In general: trains that encounter a lit railroad flare are required to stop until it burns out.[26] Fusees made specifically for railroad use can be distinguished from highway fusees by a sharp steel spike at one end, used to embed the fusee upright in a woodenrailroad tie.
In forestry and firefighting, fusees are sometimes used inwildfire suppression and in the ignition ofcontrolled burns. They ignite at 191 °C (376 °F) and burn as hot as 1,600 °C (2,910 °F).[27]
Flares are used by law enforcement agencies such as the United StatesNational Guard, and police as a form ofriot control.[28] This practice dates back to at least the 1940s where they are mentioned as being "useful in night operations".[28] Handheld flares are also counter used by protestors atdemonstrations.[29]
In 1859,Martha Coston patented the Coston flare based on early work by her deceased husband Benjamin Franklin Coston.[30]
In 1922, a "landing flare" was an aerial candle attached to a parachute and used for landing an airplane in the dark. The flare burned for less than four minutes and thecandlepower was about 40,000lumens.[31] DuringWorld War II, the U.S. Navy tested underwater flares for use in detecting submarines.[32]
A special variety of flares is used in military aircraft as a defensivecountermeasure againstheat-seeking missiles. These flares are usually discharged individually or in salvos by the pilot or automatically by tail-warning devices, and are accompanied by vigorous evasive maneuvering. Since they are intended to deceive infrared missiles, these flares burn at temperatures of thousands of degrees,incandescing in the visible spectrum as well.
Flares connected totripwires are used to guard an area against infiltration. The flare begins burning when the tripwire is triggered, providing both alarm and illumination.
Under theUN hazard number system, pyrotechnic flares are designated class 1.4 explosives.[33]
Several U.S. states, including California and Massachusetts, have begun regulating levels of potassium perchlorate, which can be unsafe at certain levels in drinking water. Contaminated drinking water can lead to such symptoms as gastric irritation, nausea, vomiting, fever, skin rashes, and even fatalaplastic anemia (a reduction in all types of blood cells).[34]
Flares produce their light through thecombustion of apyrotechnic composition. The ingredients are varied, but often based onstrontium nitrate,potassium nitrate, orpotassium perchlorate, mixed with a fuel such ascharcoal,sulfur,sawdust,aluminium,magnesium, or a suitablepolymericresin.[35] Flares may be colored by the inclusion ofpyrotechnic colorants.Calcium flares are used underwater to illuminate submerged objects.
Many in-service colored signal flares and spectrally balanceddecoy flares containperchlorateoxidizers. Perchlorate, a type ofsalt in its solid form, dissolves and moves rapidly in groundwater and surface water. Even in low concentrations in drinking water supplies, perchlorate is known to inhibit the uptake ofiodine by thethyroid gland. While there are currently no US federaldrinking water standards for perchlorate, some states have established public health goals or action levels, and some are in the process of establishing state maximum contaminant levels. For example, theUS Environmental Protection Agency has studied the impacts of perchlorate on the environment as well as drinking water.[36] California has also issued guidance regarding perchlorate use.[37]
US courts have taken action regarding the use of perchlorate in manufacturing pyrotechnic devices such as flares. For example, in 2003, a federal district court in California found that the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) applied because perchlorate is ignitable and therefore a "characteristic"hazardous waste.[38] Flares manufactured in the United States no longer usepotassium perchlorate as an oxidizer and do not containaluminium ormagnesium.[citation needed]
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