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History[ edit ] Carbon tetrachloride CCl4 was used in fire extinguishers and glass "anti-fire grenades" from the late nineteenth century until around the end of World War II. Experimentation with chloroalkanes for fire suppression on military aircraft began at least as early as the s.

Freon is a trade name for a group of CFCs which are used primarily as refrigerants , but also have uses in fire-fighting and as propellants in aerosol cans. Bromomethane is widely used as a fumigant. Dichloromethane is a versatile industrial solvent.

In the late s, Thomas Midgley, Jr. In searching for a new refrigerant, requirements for the compound were: In a demonstration for the American Chemical Society , Midgley flamboyantly demonstrated all these properties by inhaling a breath of the gas and using it to blow out a candle [6] in Nevertheless, after the war they slowly became more common in civil aviation as well.

In the s, fluoroalkanes and bromofluoroalkanes became available and were quickly recognized as being highly effective fire-fighting materials. Much early research with Halon was conducted under the auspices of the US Armed Forces, while Halon was, initially, mainly developed in the UK.

By the late s 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 s, bromofluoroalkanes also progressively came to be associated with rapid knockdown of severe fires in confined spaces with minimal risk to personnel.

By the early s, bromofluoroalkanes were in common use on aircraft, ships, and large vehicles as well as in computer facilities and galleries. However, concern was beginning to be expressed about the impact of chloroalkanes and bromoalkanes on the ozone layer. The Vienna Convention for the Protection of the Ozone Layer did not cover bromofluoroalkanes as it was thought, at the time, that emergency discharge of extinguishing systems was too small in volume to produce a significant impact, and too important to human safety for restriction.

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February Learn how and when to remove this template message Since the late s, the use of CFCs has been heavily regulated because of their destructive effects on the ozone layer. 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 over Ireland.

In a self-funded research expedition ending in , Lovelock went on to measure CFC 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 experiment did however provide the first useful data on the presence of CFCs in the atmosphere. NASA projection of stratospheric ozone, in Dobson units , if chlorofluorocarbons had not been banned. By , in response to a dramatic seasonal depletion of the ozone layer over Antarctica , diplomats in Montreal forged a treaty, the Montreal Protocol , which called for drastic reductions in the production of CFCs.

In , diplomats met in London and voted to significantly strengthen the Montreal Protocol by calling for a complete elimination of CFCs by the year By the year , CFCs should have been completely eliminated from developing countries as well.

Ozone-depleting gas trends Because the only CFCs available to countries adhering to the treaty is from recycling, their prices have increased considerably.

A worldwide end to production should also terminate the smuggling of this material. The report estimated between 7, and 14, tonnes of CFCs are smuggled annually into developing countries.

The cost of replacing the equipment of these items is sometimes cheaper than outfitting them with a more ozone-friendly appliance. Additionally, CFC smuggling is not considered a significant issue, so the perceived penalties for smuggling are low. In public attention was drawn to the issue, that at an unknown place in east Asia an estimated amount of By the time of the Montreal Protocol , it was realised that deliberate and accidental discharges during system tests and maintenance accounted for substantially larger volumes than emergency discharges, and consequently halons were brought into the treaty, albeit with many exceptions.

Regulatory gap[ edit ] While the production and consumption of CFCs are regulated under the Montreal Protocol, emissions from existing banks of CFCs are not regulated under the agreement.

In , there were an estimated 5, kilotons of CFCs in existing products such as refrigerators, air conditioners, aerosol cans and others. Regulation and DuPont[ edit ] In 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. Patent was set to expire in In conjunction with other industrial peers DuPont formed a lobbying group, the "Alliance for Responsible CFC Policy," to combat regulations of ozone-depleting compounds.

Permitted chlorofluoroalkane uses are medicinal only. 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 , based on the Montreal Protocol and guidelines of the European Union.

Production of new stocks ceased in most probably all countries in There are also a few other, highly specialized uses. These programs recycle halon through "halon banks" coordinated by the Halon Recycling Corporation [18] to ensure that discharge to the atmosphere occurs only in a genuine emergency and to conserve remaining stocks. These included Suva refrigerants and Dymel propellants. Hydrofluorocarbons are included in the Kyoto Protocol because of their very high Global Warming Potential and are facing calls to be regulated under the Montreal Protocol [ dubious discuss ] [22] due to the recognition of halocarbon contributions to climate change.

Developing nations were given until Many nations, such as the United States and China , who had previously resisted such efforts , agreed with the accelerated phase out schedule. The hydrochlorofluorocarbons HCFCs are less stable in the lower atmosphere, enabling them to break down before reaching the ozone layer.

Nevertheless, a significant fraction of the HCFCs do break down in the stratosphere and they have contributed to more chlorine buildup there than originally predicted. Later alternatives lacking the chlorine, the hydrofluorocarbons HFCs have an even shorter lifetimes in the lower atmosphere.

One of the natural refrigerants along with ammonia and carbon dioxide , hydrocarbons have negligible environmental impacts and are also used worldwide in domestic and commercial refrigeration applications, and are becoming available in new split system air conditioners.


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