Chlorofluorocarbons CFCs

[edit] Introduction

Chlorofluorocarbons (commonly referred to as CFCs) are a type of halocarbon formulated from carbon, chlorine and fluorine. Halocarbons are defined by the Intergovernmental Panel on Climate Change as ‘A collective term for the group of partially halogenated organic species which includes…chlorofluorocarbons'.

[edit] History of CFCs

CFCs were first discovered by the Belgian chemist Frédéric Swarts in the 1890s. The connection between CFCs and refrigeration was made in 1928, prompted by safety issues associated with early forms of mechanical refrigeration.

In the late 1800s and early 1900s, refrigerators used dangerous gases for cooling. The combination of ammonia (NH3), methyl chloride (CH3Cl) and sulfur dioxide (SO2) was linked to fatal accidents due to leakage, which prompted several refrigeration corporations to push for the development of a safer alternative.

In 1928, a team of researchers led by the American chemist Thomas Midgley, Jr. on behalf of General Motors (the parent company of Frigidaire - a major United States manufacturer of refrigerators) found that Swarts’ discovery could be put to practical use after some modifications were made. General Motors subsequently patented a device that used the new type of CFC, and in 1930 the company formed a division to produce the modified substance - trademarked under the name Freon - on a large commercial scale.

From the 1930s, CFCs became widely used in the United States for residential, commercial and automotive air conditioning systems. They were also commonly used as a propellant in various products - ranging from pesticides to healthcare items.

[edit] Safety of CFCs called into question

Initially, CFCs were thought to be completely safe due to their non flammable characteristics, low toxicity and stability. Furthermore, they had no impact on the lower atmosphere. However, in the 1970s, scientists discovered that the potential impact of emissions from CFCs on the upper atmosphere (or stratosphere) might be cause for concern. Research conducted by University of California chemists Professor F. Sherwood Rowland and Dr Mario Molina found that CFCs emit significant amounts of inorganic chlorine in the upper atmosphere, and this was seen as a contributing factor to ozone depletion.

[edit] CFCs and damage to the ozone layer

The high-altitude stratospheric ozone layer acts as a shield in the atmosphere, protecting life from harmful ultraviolet (UV) radiation emitted by the sun. Scientific evidence shows that certain compounds can cause considerable damage to - and weakening of - the earth’s ozone layer, leading to increases in the incidence of skin cancer and cataracts, as well as having an adverse effect on crops, plants and ocean plankton.

The use of ozone depleting chemicals such as CFCs peaked by the 1980s. But after greenhouse gas (GHG) emissions associated with CFCs were linked to the formation of the ozone hole over the Antarctic, a global effort was made to decrease the use of this (and other) fluorocarbon refrigerants.

The emission of GHGs allows sunlight to enter the atmosphere and heat the Earth’s surfaces. These surfaces then re-radiate that heat as long-wave infrared radiation, which greenhouse gases tend to absorb rather than transmit. The result is that the long-wave infrared radiation is trapped and heat accumulates in the atmosphere causing a warming process.

[edit] Ceasing the production of CFCs

The research conducted by Rowland and Molina on the decomposition of ozone (caused by CFC emissions in particular) - along with contributions from researchers at the Max Planck Institute for Chemistry - received the 1995 Nobel Prize for Chemistry. It also formed the basis of the Montreal Protocol on Substances that Deplete the Ozone Layer (the Montreal Protocol).

The Montreal Protocol was agreed on 16 September 1987 and came into effect on 1 January 1989. It came after a series of rigorous meetings and crucial negotiations at the Headquarters of the International Civil Aviation Organisation in Montreal, Quebec, in Canada and was ratified by all 196 United Nations members. Its framework was defined by the Vienna Convention for the Protection of the Ozone Layer in 1985.

It was developed to reduce the production of ozone depleting substances such as CFCs. The definition of ozone depleting substances only includes halogen source gases emitted by human activities and controlled by the Montreal Protocol. Those gases that have only natural sources are not classed as ozone depleting substances. Most ozone depleting substances are also greenhouse gases that contribute to global warming (ref United Nations Environment Programme 2010).

The Protocol introduced an incremental reduction of the manufacture, import, export and consumption of CFCs and other substances that deplete the ozone layer. In 1990, an amendment to the Protocol escalated the commitment to cease production of CFCs by 2000. In 1996, the production ban in major countries came into effect.

During the phase out, certain refrigerants were introduced as CFC substitutes. Some of these too became restricted under the Kyoto Protocol in 1997.

For more information see: HFC phase out and R22 phase out and Hydrochlorofluorocarbons HCFCs.

The Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC) is an international agreement which commits participants to internationally binding greenhouse gas emission reduction targets. It also assists countries in adapting to climate change through the Adaptation Fund by facilitating the development and deployment of technologies to increase resilience.

[edit] Related articles on Designing Buildings

• Chiller units.
• Fluorocarbon.
• Greenhouse gases.
• Halocarbons.
• HFC phase out.
• Hydrochlorofluorocarbons HCFCs.
• Intergovernmental Panel on Climate Change IPCC.
• Kyoto Protocol.
• Montreal Protocol on Substances that Deplete the Ozone Layer.
• Ozone-depleting substances.
• R22 phase out.
• Refrigerants in buildings.

[edit] External resources

• Intergovernmental Panel on Climate Change, Climate Change 2021, The Physical Science Basis.
• The 2010 Assessment of the Scientific Assessment Panel (UNEP 2010).