Carbon dioxide


Metabolic changes that occur in the body result in the generation of volatile acid, carbon dioxide, and nonvolatile acids.

Fat and carbohydrate metabolism leads to the formation of large amount of carbon dioxide.

Combines with water to form carbonic acid (H2CO3) and the lungs excrete the volatile fraction through ventilation and prevents acid accumulation.

The PaCO2 is normally maintained within the range of 35-45 mm Hg.

CO2 is a colorless gas with a density about 60% higher than that of dry air. 

Consists of a carbon atom covalently double bonded to two oxygen atoms. 

It occurs naturally in Earth’s atmosphere as a trace gas.


The current concentration is about 0.04% (412 ppm) by volume, having risen from pre-industrial levels of 280 ppm.

Carbon dioxide emissions from fossil fuels have raisins sharply in the past 70 years, reaching 35 billion metric tons of CO2 admitted in 2020, compared with just 5 billion metric tons in 1950.

Largely as a result of fossil fuel emissions, the average surface temperature of the earth has increased by approximately 1.1 C since preindustrial times.

Natural sources include: volcanoes, hot springs,geysers, and it is freed from carbonate rocks by dissolution in water and acids.


It is soluble in water, occuring naturally in groundwater, rivers and lakes, ice caps, glaciers and seawater. 


CO2 is present in deposits of petroleum and natural gas. 


Carbon dioxide is odorless at normally encountered concentrations.


At high concentrations, it has a sharp and acidic odor.


Atmospheric carbon dioxide is the primary carbon source for life on Earth.


CO2 concentration has been regulated by photosynthetic organisms and geological phenomena. 


Plants, algae and cyanobacteria use light energy to photosynthesize carbohydrate from carbon dioxide and water, with oxygen produced as a waste product.


CO2 is produced by all aerobic organisms when they metabolize carbohydrates and lipids to produce energy by respiration.


It is returned to water via the gills of fish and to the air via the lungs of air-breathing land animals.


It  is produced during the decay of organic materials and the fermentation of sugars in bread, beer and wine making, by combustion of wood and other organic materials and fossil fuels such as coal, peat, petroleum and natural gas. 


It is a  byproduct in many large scale oxidation processes.


It is an industrial material used as an inert gas in welding and fire extinguishers, as a pressurizing gas in air guns and oil recovery, as a chemical feedstock and as a supercritical fluid solvent in decaffeination of coffee and supercritical drying.


It is added to drinking water and carbonated beverages including beer and sparkling wine to add effervescence. 


The frozen solid form of CO2, dry ice, is used as a refrigerant and as an abrasive in dry-ice blasting. 


CO2 is used for the synthesis of fuels and chemicals.


It is the most significant long-lived greenhouse gas in Earth’s atmosphere. 


Its anthropogenic emissions from use of fossil fuels and deforestation have rapidly increased its concentration in the atmosphere.


Its increasing concentration has lead to global warming.


Carbon dioxide also causes ocean acidification.


CO2 dissolves in water to form carbonic acid.


When CO2 is bubbled through limewater it  precipitates calcium carbonate. 


Carbon dioxide is soluble in water, in which it reversibly forms H2CO3 (carbonic acid), which is a weak acid since its ionization in water is incomplete.


The majority of the carbon dioxide is not converted into carbonic acid, but remains as CO2 molecules, not affecting the pH.


The bicarbonate ion is amphoteric:it can act as an acid or as a base, depending on pH of the solution. 


At low concentrations it is odorless, but at sufficiently-high concentrations, it has a sharp, acidic odor.


The density of carbon dioxide is around 1.98 kg/m3, about 1.67 times that of air.


In its solid state, carbon dioxide is commonly called dry ice.



Another form of solid carbon dioxide is an amorphous glass-like solid, called carbonia.



Carbonia is produced by supercooling heated CO2 at extreme pressure in a diamond anvil. 



Carbonia glass is not stable at normal pressures and reverts to gas when pressure is released.


At temperatures and pressures above its critical point, carbon dioxide behaves as a supercritical fluid known as supercritical carbon dioxide, which used for power generation.


The combustion of all carbon-based fuels, such as methane (natural gas), petroleum distillates (gasoline, diesel, kerosene, propane), coal, wood and generic organic matter produces carbon dioxide.


It is produced by thermal decomposition of limestone, CaCO3 by heating in the manufacture of quicklime.


Iron is reduced from its oxides with coke in a blast furnace, producing pig iron and carbon dioxide.



It is a byproduct of the industrial production of hydrogen.



The reaction of water and natural gas, mainly methane, is a major source of food-grade carbon dioxide for use in carbonation of beer and soft drinks, and is also used for stunning animals such as poultry. 



The reaction of water and natural gas is accompanied by foaming or bubbling, or both, as the gas is released, and can be used to neutralize waste acid streams.



It is a by-product of the fermentation of sugar in the brewing of beer, whisky and other alcoholic beverages and in the production of Yeast metabolizes sugar to produce CO2 and ethanol.



All aerobic organisms produce CO2 when they oxidize carbohydrates, fatty acids, and proteins. 



Anaerobic organisms decompose organic material producing methane and carbon dioxide.



Carbon dioxide comprises about 40–45% of the gas that emanates from decomposition in landfills.



Most of the remaining 50–55% is methane.



One of its major uses as a chemical is in the production of carbonated beverages; it provides the sparkle in carbonated beverages such as soda water, beer and sparkling wine.



In the chemical industry, it is mainly consumed as an ingredient in the production of urea, with a smaller fraction being used to produce methanol.



Candy may be pressurized with carbon dioxide gas, and when placed in the mouth, it dissolves or releases the gas bubbles with an audible pop.



Leavening agents cause dough to rise as they produce carbon dioxide.



Baker’s yeast produces CO2 by fermentation of sugars within the dough, 



Chemical leaveners such as baking powder and baking soda release carbon dioxide when heated or exposed to acids.



The taste of soda water other carbonated beverages is an effect of the dissolved carbon dioxide.



Carbon dioxide in the form of dry ice is often used in winemaking to cool clusters of grapes quickly after picking to help prevent spontaneous fermentation by wild yeast. 



Carbon dioxide is often used to “stun” animals before slaughter.



It is  commonly used compressed gases for pneumatic systems in portable pressure tools. 



Carbon dioxide is also used as an atmosphere for welding.



It is used in many consumer products that require pressurized gas because it is inexpensive and nonflammable, and because it undergoes a phase transition from gas to liquid at room temperature at an attainable pressures.



Life jackets often contain canisters of pressured carbon dioxide for quick inflation. 



Aluminium capsules of CO2 are supplied as compressed gas for air guns, paintball markers/guns, inflating bicycle tires, and for making carbonated water. 



Rapid vaporization of liquid CO2 is used for blasting in coal mines.



High concentrations can also be used to kill pests. 



Carbon dioxide can be used to extinguish flames by starving them of oxygen.



Some fire extinguishers contain liquid carbon dioxide under pressure. 



Carbon dioxide extinguishers work well on small flammable liquid and electrical fires.



Carbon dioxide systems for fire protection of ship holds and engine rooms. 



Carbon dioxide based fire protection systems have caused several deaths, due to suffocation.



Liquid carbon dioxide is a solvent for lipophilic organic compounds and is used to remove caffeine from coffee.



It is a less toxic alternative to more solvents such as organochlorides. 



Plants require carbon dioxide to conduct photosynthesis. 



The atmospheres of greenhouses may be enriched with additional CO2 to sustain and increase the rate of plant growth.



Raising the concentration to 10,000 ppm (1%) or higher for several hours will eliminate pests such as whiteflies and spider mites in a greenhouse.

Global greenhouse gas emissions are projected to increase markedly as a result of agricultural emissions, which is greater than the summation of current global emissions from all forms of transportation.
The transportation sector currently contributes an estimated 14% of greenhouse gas emissions.



Carbon dioxide is used in enhanced oil recovery where it is injected into or adjacent to producing oil wells



Liquid and solid carbon dioxide are important refrigerants for transportation and storage of ice cream and other frozen foods. 



Solid carbon dioxide is always below −78.5 °C (−109.3 °F) at regular atmospheric pressure, and is  called dry ice and is used for small shipments where refrigeration equipment is not practical. 



Carbon dioxide is the lasing medium in a carbon dioxide laser.



Carbon dioxide can be used as a means of controlling the pH of swimming pools,and reef aquaria.



It is used  as the primary coolant in the gas-cooled reactors for nuclear power generation.



Carbon dioxide induction is used for the euthanasia of laboratory animals. 



Carbon dioxide in Earth’s atmosphere is a trace gas, currently having a global average concentration of 412 parts per million by volume or 622 parts per million by mass.



Atmospheric concentrations of carbon dioxide fluctuate slightly with the seasons.



In the Northern Hemisphere atmospheric CO2 falls during spring and summer as plants consume the gas.



During northern autumn and winter as plants go dormant or die and decay CO2 atmospheric pressures increase.



CO2 concentrations  art most strongly near the ground with much smaller variations at altitude.



In urban areas concentrations of CO2 are generally higher.



Inndoor CO2 levels can reach 10 times background levels.



PIn the 1960s, the average annual increase in CO2 levels was 35% of the 2009-2018 average.



Its concentration has risen due to human activities.



Fossil fuel combustion and deforestation have caused the atmospheric concentration of carbon dioxide to increase by about 43% since the beginning of the age of industrialization.



Human activities associated with CO2 is mostly released from burning coal and other fossil fuels. 



The other  human activities that produced CO2 include:  deforestation, biomass burning, and cement production.



Human activities emit about 29 billion tons of carbon dioxide per year.



Volcanoes emit between 0.2 and 0.3 billion tons.



Human activities have caused CO2 to increase to  levels not seen in hundreds of thousands of years. 



About half of the carbon dioxide released from the burning of fossil fuels remains in the atmosphere and is not absorbed by vegetation and the oceans.



Carbon dioxide the greenhouse gas, is absorbed and emits  infrared radiation at its two infrared-active vibrational frequencies.



Absorption of infrared light at the frequencies of atmospheric carbon dioxide traps energy near the surface, warming the surface and the lower atmosphere. 



Less energy reaches the upper atmosphere, which is therefore cooler because of this absorption.



The increases in atmospheric concentrations of CO2 and other long-lived greenhouse gases such as methane, nitrous oxide and ozone have strengthened their absorption and emission of infrared radiation, causing the rise in average global temperature since the mid-20th century. 



Carbon dioxide is of greatest concern exerts a larger overall warming influence than all of these other gases combined and because it has a long atmospheric lifetime measured in hundreds to thousands of years



Of Earths atmospheric CO2, half of global-warming emissions are not absorbed.



As carbon dioxide concentrations increase it leads to increases in global surface temperature



Increasing global temperatures causes increasing concentrations of carbon dioxide. 



The carbon dioxide concentration was 20 times greater than today, five hundred million years ago.



 The carbon dioxide concentration was decreased to 4–5 times during the Jurassic period and then slowly declining with a marked reduction occurring 49 million years ago.



Local concentrations of carbon dioxide can reach high values near strong sources.



Carbon dioxide dissolves in the ocean to form carbonic acid (H2CO3), bicarbonate (HCO3−) and carbonate (CO32−). 



There is about fifty times as much carbon dioxide dissolved in the oceans as exists in the atmosphere. 



The oceans act as an enormous carbon sink, and have taken up about a third of CO2 emitted by human activity.



As carbon dioxide increases in the atmosphere, there is  increased uptake of carbon dioxide into the oceans is causing a measurable decrease in the pH of the oceans.



The resulting pH reduction affects biological systems in the oceans, primarily oceanic calcifying organisms, effecting the food chain and include organisms such as coccolithophores, corals, foraminifera, echinoderms, crustaceans and mollusks. 



Normally calcium carbonate is stable in surface water since the carbonate ion is at supersaturating concentrations. 



When ocean pH falls, the concentration of carbonate ion drops and carbonate becomes undersaturated, causing structures made of calcium carbonated to  be vulnerable to dissolution: Corals, coccolithophore algae, coralline algae, foraminifera, shellfish and pteropods.



 In addition,  gas solubility decreases as the temperature of water increaseses, and therefore the rate of uptake from the atmosphere decreases as ocean temperatures rise.



About 30% of the total CO2 released into the atmosphere is taken up by the ocean, forming carbonic acid in equilibrium with bicarbonate. 



The decreased alkalinity of seawater, may adversely affect organisms living in the water: the availability of carbonates for forming shells decreases.



About 50% of the carbon dioxide released derived from the burning of fossil fuels, results in chemical lowering  ocean pH. 



This has caused an increased seawater in hydrogen ion of about 30%.



Since the start of the industrial age an increase in hydrogen ion is about 30%.



As increased seawater acidification occurs adverse processes occur: 


rate of  reef-building corals produce skeletons decrease, production of jellyfish increases, the ability of marine algae and plankton to maintain protective shells is reduced, and survival of larval marine species, fish and shellfish is reduced.



With active photosynthesis, plants can absorb more carbon dioxide from the atmosphere than they release in respiration.



Carbon dioxide with water, forms oxygen and organic compounds by photosynthesis, which can be respired to water and CO2.



Carbon fixation is a process by which atmospheric carbon dioxide is incorporated by plants, algae and bacteria into energy-rich organic molecules such as glucose, thus creating their own food by photosynthesis. 



Photosynthesis uses carbon dioxide and water to produce sugars from which other organic compounds can be constructed, and oxygen is produced as a by-product.



Ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) is the enzyme involved in the first major step of carbon fixation.



RuBisCO is possibly the single most abundant protein on Earth.



The products of photosynthesis are used as internal food sources and for the biosynthesis of more complex organic molecules, such as polysaccharides, nucleic acids and proteins. 



Photosynthesis products


are the basis of the food chains that feed other organisms, including animals and humans.



Plants can grow as much as 50 percent faster in concentrations of 1,000 ppm CO2 when compared with ambient conditions.



Elevated CO2 levels cause increased growth reflected in the harvestable yield of crops, with wheat, rice and soybean all showing increases in yield of 12–14% under elevated CO2.



Increased atmospheric CO2 levels concentrations results in fewer stomata on plants reducing water usage.



CO2 enrichment decreases  concentrations of micronutrients in crop plants,effecting on other parts of ecosystems that will need to eat more food to gain the same amount of protein.



The majority of plants and algae that use photosynthesis, are  net absorbers during the day. 



Forests absorb  many tons of CO2 each year, but a mature forest will produce as much CO2 from respiration and decomposition of dead specimens as is used in photosynthesis in growing plants.



Mature forests can continue to accumulate carbon and remain carbon sinks, therefor helping to maintain the carbon balance of the atmosphere. 



Photosynthesis by phytoplankton consumes dissolved CO2 in the upper ocean and promotes the absorption of CO2 from the atmosphere.



Carbon dioxide content in fresh air 


varies between 0.036% (360 ppm) and 0.041% (412 ppm), depending on the location.



CO2 is an asphyxiant gas.



CO2 is not classified as toxic or harmful.



CO2 concentrations up to 1% (10,000 ppm), can make some people feel drowsy and cause respiratory changes.



CO2 concentrations of 7% to 10% (70,000 to 100,000 ppm) may cause suffocation.



CO2 concentrations of 7% to 10% 


manifest as dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour: hypercapnia, a subset of asphyxiation.



Modified respiratory and kidney bicarbonate production are utilized to adapt to increased CO2 level effects of acidosis.



Occupational CO2 exposure limits have been set in the United States at 0.5% over an eight-hour period.



 It at such CO2 concentration, International Space Station crews have experienced headaches, lethargy, mental slowness, emotional irritation, and sleep disruption.



People exposed in 2.5 hour sessions of CO2 concentrations as low as 0.1% have  demonstrated significant negative effects on cognitive abilities, likely due to CO2 induced increases in cerebral blood flow.



One of the main causes of excessive CO2  concentrations is closed spaces. 



High CO2 concentrations are associated with impaired  health, comfort and performance.




The body produces approximately 2.3 pounds or about 1.0 kg of carbon dioxide per day per person, and contains 0.63 pounds (290 g) of carbon. 



In humans, this carbon dioxide is carried through the venous system and is breathed out through the lungs, resulting in lower concentrations in the arteries. 



The carbon dioxide content of the blood is  measured as the partial pressure.



CO2=is carried in blood in three different ways: Most of it, about 70% to 80%, is converted to bicarbonate ions HCO−


3 by the enzyme carbonic anhydrase in the red blood cells.



5–10% is dissolved in the plasma.



5–10% is bound to hemoglobin as carbamino compounds.



Hemoglobin, the main oxygen-carrying molecule in red blood cells, carries both oxygen and carbon dioxide. 



The CO2 bound to hemoglobin does not bind to the same site as oxygen: combining  with the N-terminal groups on the four globin chains. 



The  binding of CO2 decreases the amount of oxygen that is bound for a given partial pressure of oxygen. 



This Haldane Effect, is important in the transport of carbon dioxide from the tissues to the lungs. 



Conversely, a rise in the partial pressure of CO2 or a lower pH will cause offloading of oxygen from hemoglobin, which is known as the Bohr effect.



If its concentration of CO2 is high, capillaries expand to allow a greater blood flow to that tissue.



((Bicarbonate)) ions regulate  blood pH. 



The  breathing rate influences the level of CO2 in their blood: slow or shallow causes respiratory acidosis, while breathing rapidly  leads to hyperventilation, which can cause respiratory alkalosis.



Low  oxygen levels normally do not stimulate breathing, rather breathing is stimulated by higher carbon dioxide levels. 



The respiratory centers try to maintain an arterial CO2 pressure of 40 mm Hg. 



With intentional hyperventilation, the CO2 content of arterial blood may be lowered to 10–20 mm Hg, and the oxygen content of the blood is little affected, but the respiratory drive is diminished. 



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