Chloroflourocarbons were discovered in the 1920 's by Thomas Midgley , an organic chemist at General Motors Corporation . He was looking for inert , non-toxic , non-flammable compounds with low boiling points That could be used as refrigerants . He
found what he was looking for in the form of two compounds :
dichlorodifluoromethane ( CFC - 12 ) and trichloromonoflouromethane (
CFC - 11 ) . In
both compounds , different amounts of chlorine and fluorine are
combined with methane , Which is a combination of carbon and hydrogen . These two CFCs were Eventually be manufactured by EI du Pont de Nemours and Company , and , under the trade name " Freon " constituted 15 % of the market for refrigerator gases .
CFCs were the perfect answer for cooling refrigerators and air conditioners . They were easily turned into liquid at room temperature with application of just a small amount of pressure , and then they could easily be turned back into gas. CFCs were completely inert and not poisonous to humans . They Became ideal solvents for industrial solutions and hospital sterilants . Another use was found for them to blow liquid plastic into various kinds of foams .
In the 1930's , household insecticides were bulky and hard to use, so CFCs were created Because they could be kept in liquid form and in an only slightly pressurized can. Thus , in 1947 , the spray can was born , selling millions of cans each year . Insecticides were only the first application for CFC spray cans . They soon employed a number of products from deodorant to hair spray. In 1954 , 188 million cans were sold in the U.S. alone , and four years later , the number jumped to 500 million . CFC filled cans were so popular that, by 1968 , 2.3 billion spray cans were sold in America .
The hopes of a Seemingly perfect refrigerant were diminished in the late 1960's when scientists Studied the decomposition of CFCs in the atmosphere . What they found was startling . Chlorine atoms are released as the CFCs decompose , osmanthus destroying the Ozone ( O3 ) atoms in the high stratosphere . It Became Clear That human usage or CF2Cl2 and CFCl3 , and similar chemicals were causing a negative impact on the chemistry of the high-altitude air .
When CFCs and other ozone -degrading chemicals are Emitted , they mix with the atmosphere and Eventually rise to the stratosphere . CFCs themelves do not actually effect the ozone , but Their decay products do . After they photolyzed , the chlorine Eventually ends up as "reservoir species " - they do not react with ozone themelves -such as Hydrogen chloride , HCl , or Chlorine Nitrate , ClONO2 . These than further Top decompose ozone into hurting substances . The simplest is as follows : ( How do CFCs Destroy the Ozone )Cl + O3 ----- > ClO + O2 ClO + O ------ > Cl + O2 O3 + O ------- > 2 O2
The depletion of the ozone layer leads to higher levels of ultraviolet radiation reaching Earth 's surface . Therefore , this can lead to a greater number of cases of skin cancer , cataracts , and impaired immune systems , and is expected to reduce crop yields , diminish the productivity of the oceans , and possibly Contribute to the decline of amphibious populations thats occurring in the world . Besides CFCs , carbon tetrachloride , methyl bromide , methyl chloroform and halons usefull destroy the ozone .
In 1985 , the degradation of the ozone layer was confirmed when a large hole in the layer over Antarctica was reported . The hole 's existence is due to industrial chemicals All which werebe manufactured there . During September / October of 1985 , up to 60 percent of the ozone was destroyed bone . Since then , smaller yet significant stratospheric decreases have been seen on more populated regions of the Earth .
Worldwide monitoring has shown stratospheric ozone That has leg decreasing for more than 20 years . The average loss across the globe totaled about five percent since the mid- 1960's with cumulative losses of about ten percent in the winter and spring . A five percent loss Occurs in the summer and autumn in North America , Europe , and Australia .
The world has leg forced to address this issue . Thus , the major powers of the world created a global treaty , the Vienna Convention for the Protection of the Ozone Layer . The agreement was put into affect in 1988 and the Montreal Protocol on Substances Subsequent That Deplete the Ozone Layer went into effect in 1989 . To date , 140 countries are Acknowledging the Montreal Treaty . The countries Decided on a timetable for countries to reduce and to end Their production and consumption of eight major halocarbons . The timetable was accelerated in 1990 and 1992. Various amendments were ADOPTED in response to scientific evidence That stratospheric ozone is depleting at a much faster rate than was predicted .
On the home front , the U.S. Environmental Protection Agency ( EPA ) , under authority of the U.S. Clean Air Act , have issued regulations for the phase-out of production and importation of ozone depleting chemicals . The EPA established various policies zoals refrigerant recycling in both cars and stationary units , a ban on nonessential products , labeling requirements , and a requirement to revise federal procurement specifications.
One of the largest single uses of CFCs is as a refrigerant ( CFC - 12 ) used in automobile air conditioners . Since a big source of this CFC -12 is leaking automobile air conditioners , many new environmental rules have an impact on the auto service and repair industry .( 1 ) Anyone repairing or servicing motor vehicle air conditioners must recover and / or recycle CFCs on- site or recover CFCs and send them off-site for recycling .( 2 ) Everyone dealing with A / C must be certified to use CFC recovery and recycling equipment . The shop must own EPA -approved recovery and recycling equipment .( 3 ) Retailers can only sell cans of automotive refrigerant (less than 20 pounds ) to certified technicians . This discourages do-it - yourselfers from topping off Their Own A / C.
The fines for viola ting any of These rules can run as much as $ 25,000 per violation.If someone wants to keep working on A / C , they will have to make an investment in equipment . Is it worth it ? Recovery -only units cost about $ 500 and recovery / recycling units run from $ 1.800 to $ 5.000 . People working on air conditioning units must pass an EPA -approved CFC recycling course. CFC - 12 used in motor vehicles was phased out of production at the end of 1995. No more will be made .
CFCs , when first developed , were thought to be a miracle compound . They made excellent refrigerants , pesticides , deodorants , packaging foam , and had many other uses. Unfortunately, a hole in the stratosphere over Antarctica was found in 1985 , and CFCs were to blame . Since 1989 , numerous at laws and restrictions have been made to stop production of CFCs and allow the ozone in the stratosphere to replenish itself . Fortunately , the laws and restrictions have been effective and the ozone layer is slowly but surely filling in . The future of the ozone layer looks good indeed .
CFCs were the perfect answer for cooling refrigerators and air conditioners . They were easily turned into liquid at room temperature with application of just a small amount of pressure , and then they could easily be turned back into gas. CFCs were completely inert and not poisonous to humans . They Became ideal solvents for industrial solutions and hospital sterilants . Another use was found for them to blow liquid plastic into various kinds of foams .
In the 1930's , household insecticides were bulky and hard to use, so CFCs were created Because they could be kept in liquid form and in an only slightly pressurized can. Thus , in 1947 , the spray can was born , selling millions of cans each year . Insecticides were only the first application for CFC spray cans . They soon employed a number of products from deodorant to hair spray. In 1954 , 188 million cans were sold in the U.S. alone , and four years later , the number jumped to 500 million . CFC filled cans were so popular that, by 1968 , 2.3 billion spray cans were sold in America .
The hopes of a Seemingly perfect refrigerant were diminished in the late 1960's when scientists Studied the decomposition of CFCs in the atmosphere . What they found was startling . Chlorine atoms are released as the CFCs decompose , osmanthus destroying the Ozone ( O3 ) atoms in the high stratosphere . It Became Clear That human usage or CF2Cl2 and CFCl3 , and similar chemicals were causing a negative impact on the chemistry of the high-altitude air .
When CFCs and other ozone -degrading chemicals are Emitted , they mix with the atmosphere and Eventually rise to the stratosphere . CFCs themelves do not actually effect the ozone , but Their decay products do . After they photolyzed , the chlorine Eventually ends up as "reservoir species " - they do not react with ozone themelves -such as Hydrogen chloride , HCl , or Chlorine Nitrate , ClONO2 . These than further Top decompose ozone into hurting substances . The simplest is as follows : ( How do CFCs Destroy the Ozone )Cl + O3 ----- > ClO + O2 ClO + O ------ > Cl + O2 O3 + O ------- > 2 O2
The depletion of the ozone layer leads to higher levels of ultraviolet radiation reaching Earth 's surface . Therefore , this can lead to a greater number of cases of skin cancer , cataracts , and impaired immune systems , and is expected to reduce crop yields , diminish the productivity of the oceans , and possibly Contribute to the decline of amphibious populations thats occurring in the world . Besides CFCs , carbon tetrachloride , methyl bromide , methyl chloroform and halons usefull destroy the ozone .
In 1985 , the degradation of the ozone layer was confirmed when a large hole in the layer over Antarctica was reported . The hole 's existence is due to industrial chemicals All which werebe manufactured there . During September / October of 1985 , up to 60 percent of the ozone was destroyed bone . Since then , smaller yet significant stratospheric decreases have been seen on more populated regions of the Earth .
Worldwide monitoring has shown stratospheric ozone That has leg decreasing for more than 20 years . The average loss across the globe totaled about five percent since the mid- 1960's with cumulative losses of about ten percent in the winter and spring . A five percent loss Occurs in the summer and autumn in North America , Europe , and Australia .
The world has leg forced to address this issue . Thus , the major powers of the world created a global treaty , the Vienna Convention for the Protection of the Ozone Layer . The agreement was put into affect in 1988 and the Montreal Protocol on Substances Subsequent That Deplete the Ozone Layer went into effect in 1989 . To date , 140 countries are Acknowledging the Montreal Treaty . The countries Decided on a timetable for countries to reduce and to end Their production and consumption of eight major halocarbons . The timetable was accelerated in 1990 and 1992. Various amendments were ADOPTED in response to scientific evidence That stratospheric ozone is depleting at a much faster rate than was predicted .
On the home front , the U.S. Environmental Protection Agency ( EPA ) , under authority of the U.S. Clean Air Act , have issued regulations for the phase-out of production and importation of ozone depleting chemicals . The EPA established various policies zoals refrigerant recycling in both cars and stationary units , a ban on nonessential products , labeling requirements , and a requirement to revise federal procurement specifications.
One of the largest single uses of CFCs is as a refrigerant ( CFC - 12 ) used in automobile air conditioners . Since a big source of this CFC -12 is leaking automobile air conditioners , many new environmental rules have an impact on the auto service and repair industry .( 1 ) Anyone repairing or servicing motor vehicle air conditioners must recover and / or recycle CFCs on- site or recover CFCs and send them off-site for recycling .( 2 ) Everyone dealing with A / C must be certified to use CFC recovery and recycling equipment . The shop must own EPA -approved recovery and recycling equipment .( 3 ) Retailers can only sell cans of automotive refrigerant (less than 20 pounds ) to certified technicians . This discourages do-it - yourselfers from topping off Their Own A / C.
The fines for viola ting any of These rules can run as much as $ 25,000 per violation.If someone wants to keep working on A / C , they will have to make an investment in equipment . Is it worth it ? Recovery -only units cost about $ 500 and recovery / recycling units run from $ 1.800 to $ 5.000 . People working on air conditioning units must pass an EPA -approved CFC recycling course. CFC - 12 used in motor vehicles was phased out of production at the end of 1995. No more will be made .
CFCs , when first developed , were thought to be a miracle compound . They made excellent refrigerants , pesticides , deodorants , packaging foam , and had many other uses. Unfortunately, a hole in the stratosphere over Antarctica was found in 1985 , and CFCs were to blame . Since 1989 , numerous at laws and restrictions have been made to stop production of CFCs and allow the ozone in the stratosphere to replenish itself . Fortunately , the laws and restrictions have been effective and the ozone layer is slowly but surely filling in . The future of the ozone layer looks good indeed .
No comments:
Post a Comment