Chlorofluorocarbon
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propane.As a result of CFCs contributing to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs)[1] including R-410A, R-134a and R-1234yf.Because the fluorine and chlorine atoms differ greatly in size and effective charge from hydrogen and from each other, the methane-derived CFCs deviate from perfect tetrahedral symmetry.Later in the 1920s after a series of fatal accidents involving the leaking of chloromethane from refrigerators, a major collaborative effort began between American corporations Frigidaire, General Motors, and DuPont to develop a safer, non-toxic alternative.[24][25] By 1930, General Motors and Du Pont formed the Kinetic Chemical Company to produce Freon, and by 1935, over 8 million refrigerators utilizing R-12 were sold by Frigidaire and its competitors.It wasn't until 1974 that it was first discovered by two University of California chemists, Professor F. Sherwood Rowland and Dr. Mario Molina, that the use of chlorofluorocarbons were causing a significant depletion in atmospheric ozone concentrations.[27][28] During World War II, various chloroalkanes were in standard use in military aircraft, although these early halons suffered from excessive toxicity.By the late 1960s they were standard in many applications where water and dry-powder extinguishers posed a threat of damage to the protected property, including computer rooms, telecommunications switches, laboratories, museums and art collections.Beginning with warships, in the 1970s, bromofluoroalkanes also progressively came to be associated with rapid knockdown of severe fires in confined spaces with minimal risk to personnel.This is due to the fact that emergency discharge of extinguishing systems was thought to be too small in volume to produce a significant impact, and too important to human safety for restriction.After the development of his electron capture detector, James Lovelock was the first to detect the widespread presence of CFCs in the air, finding a mole fraction of 60 ppt of CFC-11 over Ireland.In a self-funded research expedition ending in 1973, Lovelock went on to measure CFC-11 in both the Arctic and Antarctic, finding the presence of the gas in each of 50 air samples collected, and concluding that CFCs are not hazardous to the environment.The damage caused by CFCs was discovered by Sherry Rowland and Mario Molina who, after hearing a lecture on the subject of Lovelock's work, embarked on research resulting in the first publication suggesting the connection in 1974.In 1990, diplomats met in London and voted to significantly strengthen the Montreal Protocol by calling for a complete elimination of CFCs by 2000.However, there are current CFC smuggling issues, as recognized by the United Nations Environmental Programme (UNEP) in a 2006 report titled "Illegal Trade in Ozone Depleting Substances".In 2018 public attention was drawn to the issue, that at an unknown place in east Asia an estimated amount of 13,000 metric tons annually of CFCs have been produced since about 2012 in violation of the protocol.[41] In 1978 the United States banned the use of CFCs such as Freon in aerosol cans, the beginning of a long series of regulatory actions against their use.In conjunction with other industrial peers DuPont formed a lobbying group, the "Alliance for Responsible CFC Policy", to combat regulations of ozone-depleting compounds.Bromofluoroalkanes have been largely phased out and the possession of equipment for their use is prohibited in some countries like the Netherlands and Belgium, from 1 January 2004, based on the Montreal Protocol and guidelines of the European Union.[44][45][46] However many countries still require aircraft to be fitted with halon fire suppression systems because no safe and completely satisfactory alternative has been discovered for this application.[56] Preventing the release of these harmful refrigerants has been ranked as one of the single most effective actions we can take to mitigate catastrophic climate change.Hydrocarbon refrigerants (a propane/isobutane blend) were also used extensively in mobile air conditioning systems in Australia, the US and many other countries, as they had excellent thermodynamic properties and performed particularly well in high ambient temperatures.[62] HFOs have an ozone depletion potential of 0.0, compared to the 1.0 of principal CFC-11, and a low GWP which make them environmentally safer alternatives to CFCs, HCFCs and HFCs.[65] The phaseout and replacement of CFCs and HFCs in the automotive industry will ultimately reduce the release of these gases to atmosphere and in turn have a positive contribution to the mitigation of climate change.Chlorofluorocarbons (CFCs) are anthropogenic compounds that have been released into the atmosphere since the 1930s in various applications such as in air-conditioning, refrigeration, blowing agents in foams, insulations and packing materials, propellants in aerosol cans, and as solvents.[71] According to their material safety data sheets, CFCs and HCFCs are colorless, volatile, non-toxic liquids and gases with a faintly sweet ethereal odor.
CFC (disambiguation)PollutionAcid rainAir quality indexAtmospheric dispersion modelingCombustionExhaust gasGlobal dimmingGlobal distillationIndoor air qualityNon-exhaust emissionsOzone depletionParticulatesPersistent organic pollutantVolatile organic compoundBiologicalBiological hazardGeneticIllegal loggingIntroduced speciesInvasive speciesInformationElectromagneticEcologicalOverilluminationRadio spectrumRadium and radon in the environmentVolcanic ashWildfireTransportationHealth effects from noiseMarine mammals and sonarNoise barrierNoise controlSoundproofingRadiationActinidesBioremediationDepleted uraniumNuclear fissionNuclear falloutPlutoniumPoisoningRadioactivityUraniumRadioactive wasteAgriculturalLand degradationDefecationElectrical resistance heatingIllegal miningSoil guideline valuesPhytoremediationAdvertising mailBiodegradable wasteBrown wasteElectronic wasteFoam food containerFood wasteGreen wasteHazardous wasteIndustrial wasteLitterMiningMunicipal solid wasteNanomaterialsPlasticPackaging wastePost-consumer wasteWaste managementSpace debrisThermalUrban heat islandVisualAir travelAdvertising clutterOverhead power linesTraffic signsUrban blightVandalismChemical warfareHerbicidal warfareAgent OrangeNuclear holocaustNuclear famineNuclear winterScorched earthUnexploded ordnanceWar and environmental lawAgricultural wastewaterBiosolidsDiseasesEutrophicationFirewaterFreshwaterGroundwaterHypoxiaIndustrial wastewaterMarineMonitoringNonpoint sourceNutrientOcean acidificationOil spillPharmaceuticalsFreshwater salinizationSeptic tanksSewageShippingSludgeStagnationSulfur waterSurface runoffTurbidityUrban runoffWater qualityWastewaterHistoryPollutantsHeavy metalsArea sourceBrain health and pollutionDebrisGarbologyLegacyMidden