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16 novembre 2011 3 16 /11 /novembre /2011 01:58

Combustion and other hazards

Highly concentrated sources of oxygen promote rapid combustion. Fire and explosion hazards exist when concentrated oxidants andfuels are brought into close proximity; however, an ignition event, such as heat or a spark, is needed to trigger combustion.Sony VAIO VPCY218EC/BI Battery

Oxygen itself is not the fuel, but the oxidant. Combustion hazards also apply to compounds of oxygen with a high oxidative potential, such as peroxides, chlorates, nitrates, perchlorates, and dichromates because they can donate oxygen to a fire.

Concentrated O2 will allow combustion to proceed rapidly and energetically.Sony VAIO VPCY218EC/G Battery

Steel pipes and storage vessels used to store and transmit both gaseous and liquid oxygen will act as a fuel; and therefore the design and manufacture of O2 systems requires special training to ensure that ignition sources are minimized. The fire that killed the Apollo 1 crew in a launch pad test spread so rapidly because the capsule was pressurized with pure O2 but at slightly more than atmospheric pressure, instead of the1?3 normal pressure that would be used in a mission.Sony VAIO VPCY218EC/L Battery

Liquid oxygen spills, if allowed to soak into organic matter, such as wood, petrochemicals, and asphalt can cause these materials to detonate unpredictably on subsequent mechanical impact. As with other cryogenic liquids, on contact with the human body it can cause frostbites to the skin and the eyes.Sony VAIO VPCY218EC/P Battery

Ozone (O3, pronounced /?o?zo?n/), or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotropeof oxygen that is much less stable than the diatomic allotrope (O2). Ozone in the lower atmosphere is an air pollutant with harmful effects on the respiratory systems of animals and will burn sensitive plants;Sony VAIO VPCY21S1E/L Battery

however, the ozone layer in the upper atmosphere is beneficial, preventing potentially damaging electromagnetic radiation from reaching the Earth's surface. Ozone is present in low concentrations throughout the Earth's atmosphere. It has many industrial and consumer applications.Sony VAIO VPCY21S1E/P Battery

History

Ozone, the first allotrope of a chemical element to be recognized, was proposed as a distinct chemical substance by Christian Friedrich Schönbein in 1840, who named it after the Greek verb ozein (?????, "to smell"), from the peculiar odor inlightning storms.Sony VAIO VPCY21S1E/SI Battery

The formula for ozone, O3, was not determined until 1865 by Jacques-Louis Soret[5] and confirmed by Schönbein in 1867.

Physical properties

Ozone is a pale blue gas, slightly soluble in water and much more soluble in inert non-polar solvents such as carbon tetrachloride or fluorocarbons, where it forms a blue solution. At 161 K (–112 °C), it condenses to form a dark blue liquid.Sony VAIO VPCZ110 Battery

It is dangerous to allow this liquid to warm to its boiling point, because both concentrated gaseous ozone and liquid ozone can detonate. At temperatures below 80 K (–193 °C), it forms a violet-black solid.

Most people can detect about 0.01 ?mol/mol of ozone in air where it has a very specific sharp odor somewhat resembling chlorine bleach.Sony VAIO VPCZ110GB/BI Battery

Exposure of 0.1 to 1 ?mol/mol produces headaches, burning eyes, and irritation to the respiratory passages. Even low concentrations of ozone in air are very destructive to organic materials such as latex, plastics, and animal lung tissue.

Ozone is diamagnetic, which means that its electrons are all paired. In contrast, O2 is paramagnetic, containing two unpaired electrons.Sony VAIO VPCZ112GD/S Battery

Structure

According to experimental evidence from microwave spectroscopy, ozone is a bent molecule, with C2v symmetry (similar to thewater molecule). The O – O distances are 127.2 pm. The O – O – O angle is 116.78°. The central atom is sp² hybridized with one lone pair. Ozone is a polar molecule with a dipole moment of 0.53 D.Sony VAIO VPCZ112GX/S Battery

The bonding can be expressed as a resonancehybrid with a single bond on one side and double bond on the other producing an overall bond order of 1.5 for each side.

Ozone in Earth's atmosphere

The standard way to express total ozone levels (the amount of ozone in a vertical column) in the atmosphere is by using Dobson units. Point measurements are reported as mole fractions in nmol/mol (parts per billion, ppb) or as concentrations in ?g/m3.Sony VAIO VPCZ114GX/S Battery

Ozone layer

The highest levels of ozone in the atmosphere are in the stratosphere, in a region also known as the ozone layer between about 10 km and 50 km above the surface (or between about 6 and 31 miles). Sony VAIO VPCZ115 Battery

Here it filters out photons with shorter wavelengths (less than 320 nm) of ultraviolet light, also called UV rays, (270 to 400 nm) from the Sun that would be harmful to most forms of lifein large doses. These same wavelengths are also among those responsible for the production of vitamin D in humans. Sony VAIO VPCZ115FC/B Battery

Ozone in the stratosphere is mostly produced from ultraviolet rays reacting with oxygen:

O2 + photon (radiation < 240 nm) ? 2 O

O + O2 + M ? O3 + M

It is destroyed by the reaction with atomic oxygen:

O3 + O ? 2 O2

The latter reaction is catalysed by the presence of certain free radicals, of which the most important are hydroxyl (OH), nitric oxide (NO) and atomic chlorine (Cl) and bromine (Br). Sony VAIO VPCZ115FC/S Battery

In recent decades the amount of ozone in the stratosphere has been declining mostly because of emissions of CFCs and similar chlorinated and brominated organic molecules, which have increased the concentration of ozone-depleting catalysts above the natural background. Ozone only makes up 0.00006% of the atmosphere.Sony VAIO VPCZ116 Battery

Low level ozone

Low level ozone (or tropospheric ozone) is an atmospheric pollutant. It is not emitted directly by car engines or by industrial operations, but formed by the reaction of sunlight on air containing hydrocarbons and nitrogen oxides that react to form ozone directly at the source of the pollution or many kilometers down wind.Sony VAIO VPCZ116GX/S Battery

Ozone reacts directly with some hydrocarbons such as aldehydes and thus begins their removal from the air, but the products are themselves key components of smog. Ozone photolysis by UV light leads to production of the hydroxyl radical OH and this plays a part in the removal of hydrocarbons from the air, Sony VAIO VPCZ117 Battery

but is also the first step in the creation of components of smog such asperoxyacyl nitrates which can be powerful eye irritants. The atmospheric lifetime of tropospheric ozone is about 22 days; its main removal mechanisms are being deposited to the ground, the above mentioned reaction giving OH, and by reactions with OH and the peroxy radical HO2· (Stevenson et al., 2006).Sony VAIO VPCZ117FC/B Battery

There is evidence of significant reduction in agricultural yields because of increased ground-level ozone and pollution which interferes with photosynthesis and stunts overall growth of some plant species. The United States Environmental Protection Agency is proposing a secondary regulation to reduce crop damage, in addition to the primary regulation designed for the protection of human health.Sony VAIO VPCZ118 Battery

Certain examples of cities with elevated ozone readings are Houston, Texas, and Mexico City, Mexico. Houston has a reading of around 41 nmol/mol, while Mexico City is far more hazardous, with a reading of about 125 nmol/mol.Sony VAIO VPCZ118GC/B Battery

Ozone cracking

Ozone gas attacks any polymer possessing olefinic or double bonds within its chain structure, such as natural rubber, nitrile rubber, and styrene-butadiene rubber. Products made using these polymers are especially susceptible to attack, which causes cracks to grow longer and deeper with time,Sony VAIO VPCZ118GX/S Battery

the rate of crack growth depending on the load carried by the product and the concentration of ozone in the atmosphere. Such materials can be protected by adding antiozonants, such as waxes, which bond to the surface to create a protective film or blend with the material and provide long term protection.Sony VAIO VPCZ119 Battery

Ozone cracking used to be a serious problem in car tires for example, but the problem is now seen only in very old tires. On the other hand, many critical products likegaskets and O-rings may be attacked by ozone produced within compressed air systems. Sony VAIO VPCZ119FJ/S Battery

Fuel lines are often made from reinforced rubber tubing and may also be susceptible to attack, especially within engine compartments where low levels of ozone are produced from electrical equipment. Storing rubber products in close proximity to DC electric motors can accelerate the rate at which ozone cracking occurs.Sony VAIO VPCZ119GC/X Battery

The commutator of the motor creates sparks which in turn produce ozone.

Ozone as a greenhouse gas

Although ozone was present at ground level before the Industrial Revolution, peak concentrations are now far higher than the pre-industrial levels, and even background concentrations well away from sources of pollution are substantially higher.Sony VAIO VPCZ119L Battery

This increase in ozone is of further concern because ozone present in the upper troposphere acts as a greenhouse gas, absorbing some of the infrared energy emitted by the earth. Quantifying the greenhouse gas potency of ozone is difficult because it is not present in uniform concentrations across the globe.Sony VAIO VPCZ119R/B Battery

However, the most widely accepted scientific assessments relating to climate change(e.g. the Intergovernmental Panel on Climate Change Third Assessment Report ) suggest that the radiative forcing of tropospheric ozone is about 25% that of carbon dioxide.Sony VAIO VPCZ119R/S Battery

The annual global warming potential of tropospheric ozone is between 918-1022 tons carbon dioxide equivalent/tons tropospheric ozone. This means on a per-molecule basis, ozone in the troposphere has a radiative forcing effect roughly 1,000 times as strong as carbon dioxide.Sony VAIO VPCZ11AFJ Battery

However, tropospheric ozone is a short-livedgreenhouse gas, which decays in the atmosphere much more quickly than carbon dioxide. This means that over a 20 year horizon, the global warming potential of tropospheric ozone is much less, roughly 62 to 69 tons carbon dioxide equivalent / tons tropospheric ozone.Sony VAIO VPCZ11AGJ Battery

Because of its short-lived nature, tropospheric ozone does not have strong global effects, but has very strong radiative forcing effects on regional scales. In fact, there are regions of the world where tropospheric ozone has a radiative forcing up to 150% of carbon dioxide.Sony VAIO VPCZ11AVJ Battery

Air pollution

Ground-level ozone is created near the Earth's surface by the action of daylight UV rays on a group of pollutants called ozone precursors. There is a great deal of evidence to show that ground level ozone can harm lung function and irritate the respiratory system.Sony VAIO VPCZ11CGX/X Battery

Exposure to ozone and the pollutants that produce it is linked to premature death, asthma, bronchitis, heart attack, and other cardiopulmonary problems.

Long-term exposure to ozone has been shown to increase risk of death from respiratory illness. Sony VAIO VPCZ11DGX/SJ Battery

A study of 450,000 people living in United States cities showed a significant correlation between ozone levels and respiratory illness over the 18-year follow-up period. The study revealed that people living in cities with high ozone levels such as Houston or Los Angeles had an over 30% increased risk of dying from lung disease.Sony VAIO VPCZ11FHX/XQ Battery

Air quality guidelines such as those from the World Health Organization, the United States Environmental Protection Agency (EPA) and the European Union are based on detailed studies designed to identify the levels that can cause measurable ill health effects.

According to scientists with the EPA, susceptible people can be adversely affected by ozone levels as low as 40 nmol/mol.Sony VAIO VPCZ11V9R/B Battery

In the EU, the current target value for ozone concentrations is 120 µg/m³ which is about 60 nmol/mol. This target applies to all member states in accordance with Directive 2008/50/EC. Ozone concentration is measured as a maximum daily mean of 8 hour averages and the target should not be exceeded on more than 25 calendar days per year, starting from January 2010. Sony VAIO VPCZ11X9E/B Battery

Whilst the directive requires in the future a strict compliance with 120 µg/m³ limit (i.e. mean ozone concentration not to be exceeded on any day of the year), there is no date set for this requirement and this is treated as a long-term objective. Sony VAIO VPCZ11Z9E/B Battery

The Clean Air Act directs the EPA to set National Ambient Air Quality Standards for several pollutants, including ground-level ozone, and counties out of compliance with these standards are required to take steps to reduce their levels. In May 2008, the EPA lowered its ozone standard from 80 nmol/mol to 75 nmol/mol. Sony VAIO VPCZ125GX/S Battery

This proved controversial, since the Agency's own scientists and advisory board had recommended lowering the standard to 60 nmol/mol, and the World Health Organization recommends 51 nmol/mol. Many public health and environmental groups also supported the 60 nmol/mol standard.Sony VAIO VPCZ127FC Battery

On January 7, 2010, the U.S. Environmental Protection Agency (EPA) announced proposed revisions to the National Ambient Air Quality Standard (NAAQS) for the pollutant ozone, the principal component of smog:

... EPA proposes that the level of the 8-hour primary standard, which was set at 0.075 ?mol/mol in the 2008 final rule, should instead be set at a lower level within the range of 0.060 to 0.070 ?mol/mol,Sony VAIO VPCZ128GC Battery

to provide increased protection for children and other ‘‘at risk’’ populations against an array of O3- related adverse health effects that range from decreased lung function and increased respiratory symptoms to serious indicators of respiratory morbidity including emergency department visits and hospital admissions for respiratory causes,Sony VAIO VPCZ12M9E/B Battery

and possibly cardiovascular-related morbidity as well as total non- accidental and cardiopulmonary mortality...

The EPA has developed an Air Quality Index (AQI) to help explain air pollution levels to the general public. Under the current standards, eight-hour average ozone mole fractions of 85 to 104 nmol/mol are described as "unhealthy for sensitive groups," 105 nmol/mol to 124 nmol/mol as "unhealthy," and 125 nmol/mol to 404 nmol/mol as "very unhealthy."Sony VAIO VPCZ13M9E/B Battery

Ozone can also be present in indoor air pollution, partly as a result of electronic equipment such as photocopiers. A connection has also been known to exist between the increased pollen, fungal spores, and ozone caused by thunderstorms and hospital admissions of asthma sufferers.Sony VAIO VPCZ13V9E/X Battery

In the Victorian era, one British folk myth held that the smell of the sea was caused by ozone. In fact, the characteristic "smell of the sea" is caused by dimethyl sulfide a chemical generated by phytoplankton. Victorian British folk considered the resulting smell "bracing," but in high concentrations, dimethyl sulfide is actually toxic.Sony VAIO VPCZ13Z9E/X Battery

Physiology

Ozone, along with reactive forms of oxygen such as superoxide, singlet oxygen, hydrogen peroxide, and hypochlorite ions, is naturally produced by white blood cellsand other biological systems (such as the roots of marigolds) as a means of destroying foreign bodies. Ozone reacts directly with organic double bonds. Sony VAIO VPCZZZHJ Battery

Also, when ozone breaks down to dioxygen it gives rise to oxygen free radicals, which are highly reactive and capable of damaging many organic molecules. Moreover, it is believed that the powerful oxidizing properties of ozone may be a contributing factor of inflammation. Sony VAIO VPZ117 Battery

The cause-and-effect relationship of how the ozone is created in the body and what it does is still under consideration and still subject to various interpretations, since other body chemical processes can trigger some of the same reactions. A team headed by Dr. Paul Wentworth Jr. of the Department of Chemistry at the Scripps Research Institute has shown evidence linking the antibody-catalyzed water-oxidation pathway of the human immune response to the production of ozone. Sony VAIO VPZ118 Battery

In this system, ozone is produced by antibody-catalyzed production oftrioxidane from water and neutrophil-produced singlet oxygen.

When inhaled, ozone reacts with compounds lining the lungs to form specific, cholesterol-derived metabolites that are thought to facilitate the build-up and pathogenesis of atherosclerotic plaques (a form of heart disease).Sony VAIO VPZ119 Battery

These metabolites have been confirmed as naturally occurring in human atherosclerotic arteries and are categorized into a class of secosterols termed atheronals, generated by ozonolysis of cholesterol's double bond to form a 5,6 secosterol as well as a secondary condensation product via aldolization.Sony VPCM11M1E/B Battery

Ozone has been implicated to have an adverse effect on plant growth: "... ozone reduced total chlorophylls, carotenoid and carbohydrate concentration, and increased 1-aminocyclopropane-1-carboxylic acid (ACC) content and ethylene production.Sony VPCM11M1E/W Battery

In treated plants, the ascorbate leaf pool was decreased, while lipid peroxidation and solute leakage were significantly higher than in ozone-free controls. The data indicated that ozone triggered protective mechanisms against oxidative stress in citrus."

Safety regulations

Due to the strongly oxidizing properties of ozone, ozone is a primary irritant, affecting especially the eyes and respiratory systems and can be hazardous at even low concentrations. Sony VPCM12M1E/L Battery

The Canadian Center for Occupation Safety and Health reports that:

"Even very low concentrations of ozone can be harmful to the upper respiratory tract and the lungs. The severity of injury depends on both by the concentration of ozone and the duration of exposure. Severe and permanent lung injury or death could result from even a very short-term exposure to relatively low concentrations." Sony VPCM12M1E/P Battery

To protect workers potentially exposed to ozone, U.S. Occupational Safety and Health Administration has established a permissible exposure limit (PEL) of 0.1 ?mol/mol (29 CFR 1910.1000 table Z-1), calculated as an 8 hour time weighted average. Sony VPCM12M1E/W Battery

Higher concentrations are especially hazardous and NIOSH has established an Immediately Dangerous to Life and Health Limit (IDLH) of 5 ?mol/mol. Work environments where ozone is used or where it is likely to be produced should have adequate ventilation and it is prudent to have a monitor for ozone that will alarm if the concentration exceeds the OSHA PEL. Sony VPCM13M1E/L Battery

Continuous monitors for ozone are available from several suppliers.

Elevated ozone exposure can occur on passenger aircraft, with levels depending on altitude and atmospheric turbulence.  United States Federal Aviation Authorityregulations set a limit of 250 nmol/mol with a maximum four-hour average of 100 nmol/mol.Sony VPCM13M1E/P Battery

Some planes are equipped with ozone converters in the ventilation system to reduce passenger exposure.

Production

Ozone often forms in nature under conditions where O2 will not react. Ozone used in industry is measured in ?mol/mol (ppm, parts per million), nmol/mol (ppb, parts per billion), ?g/m3, mg/hr (milligrams per hour) or weight percent. Sony VPCM13M1E/W Battery

The regime of applied concentrations ranges from 1 to 5% in air and from 6 to 14% in oxygen for older generation methods. New electrolytic methods can achieve up 20 to 30% dissolved ozone concentrations in output water.

Temperature and humidity plays a large role in how much ozone is being produced using traditional generation methods such as corona discharge and ultraviolet light. Sony VAIO VGN-Z11MN/B Battery

Old generation methods will produce less than 50% its nominal capacity if operated with humid ambient air than when it operates in very dry air. New generators using electrolytic methods can achieve higher purity and dissolution through using water molecules as the source of ozone production.Sony VAIO VGN-Z11VN/X Battery

Corona discharge method

This is the most common type of ozone generator for most industrial and personal uses. While variations of the "hot spark" coronal discharge method of ozone production exist, including medical grade and industrial grade ozone generators, these units usually work by means of a corona discharge tube.Sony VAIO VGN-Z11WN/B Battery

They are typically cost-effective and do not require an oxygen source other than the ambient air to produce ozone concentrations of 3-6%. Fluctuations in ambient air, due to weather or other environmental conditions, cause variability in ozone production. However, they also produce nitrogen oxides as a by-product. Sony VAIO VGN-Z11XN/B Battery

Use of an air dryer can reduce or eliminate nitric acid formation by removing water vapor and increase ozone production. Use of an oxygen concentrator can further increase the ozone production and further reduce the risk of nitric acid formation by removing not only the water vapor, but also the bulk of the nitrogen.Sony VAIO VGN-Z15 Battery

Ultraviolet light

UV ozone generators, or vacuum-ultraviolet (VUV) ozone generators, employ a light source that generates a narrow-band ultraviolet light, a subset of that produced by the Sun. The Sun's UV sustains the ozone layer in the stratosphere of Earth.Sony VAIO VGN-Z15N Battery

While standard UV ozone generators tend to be less expensive, they usually produce ozone with a concentration of about 0.5% or lower. Another disadvantage of this method is that it requires the air (oxygen) to be exposed to the UV source for a longer amount of time, and any gas that is not exposed to the UV source will not be treated.Sony VAIO VGN-Z17 Battery

This makes UV generators impractical for use in situations that deal with rapidly moving air or water streams (in-duct airsterilization, for example). Production of ozone is one of the potential dangers of ultraviolet germicidal irradiation. VUV ozone generators are used in swimming pool and spa applications ranging to millions of gallons of water.Sony VAIO VGN-Z17N Battery

VUV ozone generators, unlike corona discharge generators, do not produce harmful nitrogen by-products and also unlike corona discharge systems, VUV ozone generators work extremely well in humid air environments. There is also not normally a need for expensive off-gas mechanisms, and no need for air driers or oxygen concentrators which require extra costs and maintenance.Sony VAIO VGN-Z19 Battery

Cold plasma

In the cold plasma method, pure oxygen gas is exposed to a plasma created by dielectric barrier discharge. The diatomic oxygen is split into single atoms, which then recombine in triplets to form ozone.

Cold plasma machines utilize pure oxygen as the input source and produce a maximum concentration of about 5% ozone. Sony VAIO VGN-Z19N Battery

They produce far greater quantities of ozone in a given space of time compared to ultraviolet production. However, because cold plasma ozone generators are very expensive, they are found less frequently than the previous two types.

The discharges manifest as filamentary transfer of electrons (micro discharges) in a gap between two electrodes. Sony VAIO VGN-Z21MN/B Battery

In order to evenly distribute the micro discharges, a dielectric insulator must be used to separate the metallic electrodes and to prevent arcing.

Some cold plasma units also have the capability of producing short-lived allotropes of oxygen which include O4, O5, O6, O7, etc. These species are even more reactive than ordinary O3. Sony VAIO VGN-Z21VN/X Battery

Electrolytic

Electrolytic ozone generation (EOG) splits water molecules into H2, O2, and O3. In most EOG methods, the hydrogen gas will be removed to leave oxygen and ozone as the only reaction products. Therefore, EOG can achieve higher dissolution in water without other competing gases found in corona discharge method, such as nitrogen gases present in ambient air.Sony VAIO VGN-Z21WN/B Battery

This method of generation can achieve concentrations of 20-30% and is independent of air quality because water is used as the starting substrate.

Special considerations

Ozone cannot be stored and transported like other industrial gases (because it quickly decays into diatomic oxygen) and must therefore be produced on site. Sony VAIO VGN-Z21XN Battery

Available ozone generators vary in the arrangement and design of the high-voltage electrodes. At production capacities higher than 20 kg per hour, a gas/water tube heat-exchanger may be utilized as ground electrode and assembled with tubular high-voltage electrodes on the gas-side. Sony VAIO VGN-Z21ZN/X Battery

The regime of typical gas pressures is around 2 barabsolute in oxygen and 3 bar absolute in air. Several megawatts of electrical power may be installed in large facilities, applied as one phase AC current at 50 to 8000 Hz and peak voltages between 3,000 and 20,000 volts. Applied voltage is usually inversely related to the applied frequency.Sony VAIO VGN-Z25 Battery

The dominating parameter influencing ozone generation efficiency is the gas temperature, which is controlled by cooling water temperature and/or gas velocity. The cooler the water, the better the ozone synthesis. The lower the gas velocity, the higher the concentration (but the lower the net ozone produced). Sony VAIO VGN-Z25/B Battery

At typical industrial conditions, almost 90% of the effective power is dissipated as heat and needs to be removed by a sufficient cooling water flow.

Because of the high reactivity of ozone, only few materials may be used like stainless steel (quality 316L), titanium, aluminium (as long as no moisture is present),glass, polytetrafluorethylene, or polyvinylidene fluoride. Sony VAIO VGN-Z25TN/B Battery

Viton may be used with the restriction of constant mechanical forces and absence of humidity (humidity limitations apply depending on the formulation). Hypalon may be used with the restriction that no water come in contact with it, except for normal atmospheric levels.Sony VAIO VGN-Z26TN/B Battery

Embrittlement or shrinkage is the common mode of failure of elastomers with exposure to ozone. Ozone cracking is the common mode of failure of elastomer seals like O-rings.

Silicone rubbers are usually adequate for use as gaskets in ozone concentrations below 1 wt%, such as in equipment for accelerated aging of rubber samples.Sony VAIO VGN-Z27 Battery

Incidental production

Ozone may be formed from O2 by electrical discharges and by action of high energy electromagnetic radiation. Unsuppressed arcing breaks down the chemical bonds of the atmospheric oxygen surrounding the contacts [O2 ? 2O]. Free ions of oxygen in and around the arc recombine to create ozone [O3].Sony VAIO VGN-Z27/B Battery

Certain electrical equipmentgenerate significant levels of ozone. This is especially true of devices using high voltages, such as ionic air purifiers, laser printers, photocopiers, tasers andarc welders. Electric motors using brushes can generate ozone from repeated sparking inside the unit. Sony VAIO VGN-Z27TN/X Battery

Large motors that use brushes, such as those used by elevators or hydraulic pumps, will generate more ozone than smaller motors. Ozone is similarly formed in the Catatumbo lightning storms phenomenon on the Catatumbo River inVenezuela, which helps to replenish ozone in the upper troposphere. Sony VAIO VGN-Z29N Battery

It is the world's largest single natural generator of ozone, lending calls for it to be designated a UNESCO World Heritage Site.

Laboratory production

In the laboratory, ozone can be produced by electrolysis using a 9 volt battery, a pencil graphite rod cathode, a platinum wire anode and a 3 molar sulfuric acidelectrolyte.  The half cell reactions taking place are:Sony VAIO VGN-Z29N/X Battery

3 H2O ? O3 + 6 H+ + 6 e? (?Eo = ?1.53 V)

6 H+ + 6 e? ? 3 H2 (?Eo = 0 V)

2 H2O ? O2 + 4 H+ + 4 e? (?Eo = ?1.23 V)

In the net reaction, three equivalents of water are converted into one equivalent of ozone and three equivalents of hydrogen. Oxygen formation is a competing reaction.Sony VAIO VGN-Z31MN/B Battery

It can also be "prepared" by high voltage arc. This can be done with an apparatus consisting of two concentric glass tubes sealed together at the top, with in and out spigots at the top and bottom of the outer tube. The inner core should have a length of metal foil inserted into it connected to one side of the power source. Sony VAIO VGN-Z31VN/X Battery

The other side of the power source should be connected to another piece of foil wrapped around the outer tube. Dry O2 should be run through the tube in one spigot. As the O2 is run through one spigot into the apparatus and high voltage is applied to the foil leads, electricity will discharge between the dry dioxygen in the middle and form O3 and O2 out the other spigot. Sony VAIO VGN-Z31WN/B Battery

The reaction can be summarized as follows:

Industry

The largest use of ozone is in the preparation of pharmaceuticals, synthetic lubricants, and many other commercially useful organic compounds, where it is used to sever carbon-carbon bonds.  It can also be used for bleaching substances and for killing microorganisms in air and water sources.Sony VAIO VGN-Z31ZN/X Battery

Many municipal drinking water systems kill bacteria with ozone instead of the more common chlorine. Ozone has a very high oxidation potential. Ozone does not form organochlorine compounds, nor does it remain in the water after treatment. Ozone can form the suspected carcinogen [bromate] in source water with high bromide concentrations.Sony VAIO VGN-Z35 Battery

The Safe Drinking Water Act mandates that these systems introduce an amount of chlorine to maintain a minimum of 0.2 ?mol/mol residual free chlorine in the pipes, based on results of regular testing. Where electrical power is abundant, ozone is a cost-effective method of treating water, since it is produced on demand and does not require transportation and storage of hazardous chemicals.Sony VAIO VGN-Z35/B Battery

Once it has decayed, it leaves no taste or odor in drinking water.

Although low levels of ozone have been advertised to be of some disinfectant use in residential homes, the concentration of ozone in dry air required to have a rapid, substantial effect on airborne pathogens exceeds safe levels recommended by the U.S. Sony VAIO VGN-Z35TN/B Battery

Occupational Safety and Health Administration and Environmental Protection Agency. Humidity control can vastly improve both the killing power of the ozone and the rate at which it decays back to oxygen (more humidity allows more effectiveness). Spore forms of most pathogens are very tolerant of atmospheric ozone in concentrations where asthma patients start to have issues.Sony VAIO VGN-Z36GD Battery

Industrially, ozone is used to:

  • Disinfect laundry in hospitals, food factories, care homes etc.;
  • Disinfect water in place of chlorine
  • Deodorize air and objects, such as after a fire. This process is extensively used in fabric restoration
  • Kill bacteria on food or on contact surfaces;Sony VAIO VGN-Z36GD/B Battery
  • Sanitize swimming pools and spas
  • Kill insects in stored grain
  • Scrub yeast and mold spores from the air in food processing plants;
  • Wash fresh fruits and vegetables to kill yeast, mold and bacteria;
  • Chemically attack contaminants in water (iron, arsenic, hydrogen sulfide, nitrites, and complex organics lumped together as "colour");Sony VAIO VGN-Z36GD/J Battery
  • Provide an aid to flocculation (agglomeration of molecules, which aids in filtration, where the iron and arsenic are removed);
  • Manufacture chemical compounds via chemical synthesis
  • Clean and bleach fabrics (the former use is utilized in fabric restoration; the latter use is patented);
  • Assist in processing plastics to allow adhesion of inks;Sony VAIO VGN-Z36TD/B Battery
  • Age rubber samples to determine the useful life of a batch of rubber;
  • Eradicate water borne parasites such as Giardia lamblia and Cryptosporidium in surface water treatment plants.

Ozone is a reagent in many organic reactions in the laboratory and in industry. Ozonolysis is the cleavage of an alkene to carbonyl compounds.Sony VAIO VGN-Z36TD/J Battery

Many hospitals in the U.S. and around the world use large ozone generators to decontaminate operating rooms between surgeries. The rooms are cleaned and then sealed airtight before being filled with ozone which effectively kills or neutralizes all remaining bacteria.Sony VAIO VGN-Z37D Battery

Ozone is used as an alternative to chlorine or chlorine dioxide in the bleaching of wood pulp. It is often used in conjunction with oxygen and hydrogen peroxide to eliminate the need for chlorine-containing compounds in the manufacture of high-quality, white paper.Sony VAIO VGN-Z37D/B Battery

Ozone can be used to detoxify cyanide wastes (for example from gold and silver mining) by oxidizing cyanide to cyanate and eventually to carbon dioxide.

Consumers

Devices generating high levels of ozone, some of which use ionization, are used to sanitize and deodorize uninhabited buildings, rooms, ductwork, woodsheds, and boats and other vehicles.Sony VAIO VGN-Z37GD Battery

In the U.S., air purifiers emitting low levels of ozone have been sold. This kind of air purifier is sometimes claimed to imitate nature's way of purifying the air  without filters and to sanitize both it and household surfaces. The United States Environmental Protection Agency (EPA) has declared that there is "evidence to show that at concentrations that do not exceed public health standards,Sony VAIO VGN-Z37GD/X Battery

ozone is not effective at removing many odor-causing chemicals" or "viruses, bacteria, mold, or other biological pollutants." Furthermore, its report states that "results of some controlled studies show that concentrations of ozone considerably higher than these [human safety] standards are possible even when a user follows the manufacturer’s operating instructions."Sony VAIO VGN-Z39D Battery

The government successfully sued one company in 1995, ordering it to stop repeating health claims without supporting scientific studies.

Ozonated water is used to launder clothes and to sanitize food, drinking water, and surfaces in the home. According to the U.S. Sony VAIO VGN-Z39D/X Battery

Food and Drug Administration (FDA), it is "amending the food additive regulations to provide for the safe use of ozone in gaseous and aqueous phases as an antimicrobial agent on food, including meat and poultry." Studies at California Polytechnic University demonstrated that 0.3 ?mol/mol levels of ozone dissolved in filtered tapwater can produce a reduction of more than 99.99% in such food-borne microorganisms as salmonella, E. coli 0157:H7, and Campylobacter.Sony VAIO VGN-Z41MD/B Battery

This quantity is 20,000 times the WHO recommended limits stated above.Ozone can be used to remove pesticide residues from fruits and vegetables.

Ozone is used in homes and hot tubs

to kill bacteria in the water and to reduce the amount of chlorine or bromine required by reactivating them to their free state. Sony VAIO VGN-Z41WD/B Battery

Since ozone does not remain in the water long enough, ozone by itself is ineffective at preventing cross-contamination among bathers and must be used in conjunction with halogens. Gaseous ozone created by ultraviolet light or by corona discharge is injected into the water.Sony VAIO VGN-Z45GD/B Battery

Ozone is also widely used in treatment of water in aquariums and fish ponds. Its use can minimize bacterial growth, control parasites, eliminate transmission of some diseases, and reduce or eliminate "yellowing" of the water. Ozone must not come in contact with fish's gill structures. Sony VAIO VGN-Z45TD/B Battery

Natural salt water (with life forms) provides enough "instantaneous demand" that controlled amounts of ozone activate bromide ion to hypobromous acid, and the ozone entirely decays in a few seconds to minutes. If oxygen fed ozone is used, the water will be higher in dissolved oxygen, fish's gill structures will atrophy and they will become dependent on higher dissolved oxygen levels.Sony VAIO VGN-Z46GD/B Battery

Aquaculture

Ozone can be used in aquaculture to facilitate organic breakdown. It is added to recirculating systems to reduce nitrite levels through conversion into nitrate. If nitrite levels in the water are high, nitrites will also accumulate in the blood and tissues of fish, where it interferes with oxygen transport (it causes oxidation of the heme-group of haemoglobin from ferrous(Fe2+) to ferric (Fe3+), making haemoglobin unable to bind O2 ).Sony VAIO VGN-Z46GD/U Battery

Despite these apparent positive effects, ozone use in recirculation systems has been linked to reducing the level of bioavailable iodine in salt water systems, resulting in iodine deficiency symptoms such as goitre and decreased growth in Senegalese sole (Solea senegalensis) larvae.Sony VAIO VGN-Z46MD/B Battery

Ozonate seawater is used for surface disinfection of haddock and Atlantic halibut eggs against nodavirus. Nodavirus is a lethal and vertically transmitted virus which causes severe mortality in fish. Haddock eggs should not be treated with high ozone level as eggs so treated did not hatch and died after 3–4 days.Sony VAIO VGN-Z46SD/B Battery

Agriculture

Ozone application on freshly cut pineapple and banana shows increase in flavonoids and total phenol contents when exposure is up to 20 minutes. Decrease in ascorbic acid content is observed but the positive effect on total phenol content and flavonoids can overcome the negative effect.Sony VAIO VGN-Z46TD/B Battery

Tomatoes upon treatment with ozone shows an increase in ?-carotene, lutein and lycopene.However, ozone application on strawberries in pre-harvest period shows decrease in ascorbic acid content.

Ozone facilitates the extraction of some heavy metals from soil using EDTA. EDTA forms strong, water-soluble coordination compounds with some heavy metals (Pb, Zn) thereby making it possible to dissolve them out from contaminated soil. Sony VAIO VGN-Z46TD/R Battery

If contaminated soil is pre-treated with ozone, the extraction efficacy of Pb, Am and Puincreases by 11-28.9%, 43.5% and 50.7% respectively.Sony VAIO VGN-Z47GD/X Battery,Sony VAIO VGN-Z48GD/X Battery,Sony VAIO VGN-Z48TD/X Battery,Sony VAIO VGN-Z51WG/B Battery,Sony VAIO VGN-Z51XG/B Battery

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gas plumbing 08/07/2012 05:03

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