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Stack is nothing but chimney which is used to disperse the hot air at a great height, emissions & particulate matters that are emitted from the various types of stacks like boiler, flue gas etc. At these heights the polluted air disperses in a very large area so that concentrations at ground are within permissible limits and not harmful for humans, animals and vegetation. There are several types of flue-gas stack based on fuel injections. E.g. DG set stack, flue gas stack, process stack, furnace stack, boiler stack, chimney etc.

  • Suspended Particulate Matter – SPM (PM0.3, PM1.0, PM2.5 & PM10)

    The most common pollutant involved in fugitive emissions is dust or particulate matter PM. This is released during certain operations such as transport and open storage of solid materials and from exposed soil surfaces including unpaved roads.

    Particulate matter, also known as particle pollution or PM is a complex mixture of extremely small particles   and liquid droplets. Particle pollution is made up of a number of components including acids such as nitrates and sulfates, organic chemicals, metals and soil or dust particles.

    The size of particles is directly linked to their potential for causing health problems. USEPA, EHO and DoE are concerned about particles that 10 micrometers in diameter or smaller because those are the particles that generally pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects. Particle pollution has been grouped into two categories.

    Inhalable coarse particles such as those found near roadways and dusty industries are larger than 2.5 micrometers and smaller than 10 micrometers in diameter

    Fine particles such as those found in smoke and haze are 2.5 micrometers in diameter and smaller. These particles can be directly emitted from sources such as forest fires or they can from when gases emitted from power plants, industries and automobiles react in the air.

  • Oxygen (O2)

    Many major classes of organic molecules in living organisms such as proteins, nucleic acids, carbohydrates and fats, contain oxygen as do the major inorganic compounds that are constituents of animal shells, teeth and bone. Most of the mass of living organisms is oxygen as it is a part of water, the major constituent of life forms. Elemental oxygen is produced by cyanobacteria, algae and plants and is used in cellular respiration for all complex life.

    Oxygen is an important part of the atmosphere and necessary to sustain most terrestrial life as it is used in respiration. However, it is too chemically reactive to remain a free element in earth atmosphere without being continuously replenished by the photosynthetic action of living organisms which use the energy of sunlight to produce elemental oxygen from water.

    The combustion of a carbon-based fuel consumes oxygen. The 21% oxygen content present in the combustion air that is fed to a furnace will be depleted to some lower level in the exhaust gas. The interpretation clause of IPPC licenses typically requires emission data to be reported at reference oxygen conditions that are defined according the fuel type for example:

    • Gas and liquid fuels 3% ref O
    • Solid and liquid 6% O2
    • Waste incineration 11% ref O2
    • Other fuels (e.g. fume thermal oxidizer): The application of reference conditions will be determined on a case by case basis.
    • Emissions from all sources: Temperature 273.15˚K, pressure 101.32kpa (no correction for oxygen or water content). May apply to the wood panel industry which have combustion plants as an integral part of the drying process and necessarily dilute with ambient air to affect control of the drying process.


    The combustion of a carbon-based fuel consumes oxygen. The 21% oxygen content present in the combustion air that is fed to a furnace will be depleted to some lower level in the exhaust gas. The interpretation clause of IPPC (Intergovernmental Panel on Climate Change) license typically requires emission data to be reported at reference oxygen conditions that are defined according to the fuel type like-

    • Gas and liquid fuels 3% ref O
    • Solid fuels 6% ref O
    • Waste incineration 11% ref O
    • Other fuels (e.g. fume thermal oxidizer) – The application of reference oxygen.
  • Carbon Monoxide (CO)

    Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline, petrol, bio-diesel blends, diesel fuel, fuel oil, or coal. According to the type of Combustionngine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack, or propelling nozzle. It often disperses downwind in a pattern called an exhaust plume.

    It is a major component of motor vehicle emissions (and from stationary internal combustion engines), which can also include:

    • Crankcaseblow-by
    • Evaporation of unused gasoline

    Motor vehicle emissions contribute to air pollution and are a major ingredient in the creation of smog in some large cities. A 2013 study by MIT indicates that 53,000 early deaths occur per year in the United States alone because of vehicle emissions. According to another study from the same university, traffic fumes alone cause the death of 5,000 people every year just in the United Kingdom.

    Carbon monoxide is a colorless, odorless, poisonous gas formed when carbon in fuels is not burned completely. It is a byproduct of highway vehicle exhaust which contributes about 60 percent of all CO emissions nationwide. In cities automobile exhaust can cause as much as 95 percent of all CO emissions. These emissions can result in high concentrations of CO2 particularly in local areas with heavy traffic congestion. Other sources of CO emissions include industrial processes and fuel combustion in sources such as generators and incinerators. Despite an overall downward trend in concentrations and emissions of CO2 some metropolitan areas still experience high levels of CO2.

  • Nitrogen Dioxide (NO2)

    Nitrogen dioxide belongs to a family of highly reactive gases called nitrogen oxides (NOx). These gases form when fuel is burned at high temperatures? and come principally from motor vehicle exhaust and stationary sources such as electric utilities and industrial Generators. A suffocating, brownish gas, nitrogen dioxide is a strong oxidizing agent that reacts in the air to form corrosive nitric acid, as well as toxic organic nitrates. It also plays a major role in the atmospheric reactions that produce ground-level ozone (or smog).

  • Carbon Dioxide (CO2)

    Carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities. In 2012. CO2 accounted for about 82% of all U.S. greenhouse gas emissions from human activities. Carbon dioxide is naturally present in the atmosphere as part of the Earth’s carbon cycle (the natural circulation of carbon among the atmosphere, oceans, soil, plants, and animals). Human activities are altering the carbon cycle-both by adding more CO2 to the atmosphere and by influencing the ability of natural sinks, like forests, to remove CO2 from the atmosphere. While CO2 emissions come from a variety of natural sources, human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution.

    The main human activity that emits CO2 is the combustion of fossil fuels (coal, natural gas, and oil) for energy and transportation, although certain industrial processes and land-use changes also emit CO2.

  • Nitric Oxide (NOx)

    NOx gases are usually produced from the reaction among nitrogen and oxygen during combustion of fuels, such as hydrocarbons, in air; especially at high temperatures, such as occur in car engines.  In areas of high motor vehicle traffic, such as in large cities, the nitrogen oxides emitted can be a significant source of air pollution. NOx gases are also produced naturally by lightning. The term NOx is chemistry shorthand for molecules containing one nitrogen and one or more oxygen atom. It is generally meant to include nitrous oxide (N2O), although nitrous oxide is a fairly inert oxide of nitrogen that has many uses as an oxidizer for rockets and car engines, an anesthetic, and a propellant for aerosol sprays and whipped cream. Nitrous oxide plays hardly any role in air pollution, although it may have a significant impact on the ozone layer, and is a significant greenhouse gas. NOX (reactive, free radical) is defined as the sum of NOx plus the NOX compounds produced from the oxidation of NOx which include nitric acid.

  • Nitrogen Oxide (NO)

    Nature and Source of pollutant; NOx is a generic term for the mono-nitrogen oxides NO and NO2 (nitric oxide and nitrogen dioxide). They are produced from the reaction of nitrogen and oxygen gases in the air during combustion and high temperatures. In areas of high motor vehicle traffic, such as in large cities, the amount of nitrogen oxides emitted into the atmosphere as air pollution can be significant. NOx gases are formed whenever combustion occurs in the presence of nitrogen – as in an air-breathing engine; they also are produced naturally by lightning, atmospheric chemistry, the term means the total concentration of NO and NO2. NOx gases react to form smog and acid rain as well as being central to the formation of tropospheric ozone.

  • Sulfur Dioxide (SO2)

    Sulfur dioxide (SO2) is a gas primarily emitted from fossil fuel combustion at power plants and other industrial facilities, as well as fuel combustion in mobile sources such as locomotives, ships, and other equipment. Over 100,000 tons of SO2 were emitted in 2009 in Minnesota. Current scientific evidence links SO2 exposure with adverse impacts on the respiratory system. In recent reviews of the standard, EPA has determined that even short-term exposure to high levels of SO2 can have a detrimental effect on breathing function, particular for those that suffer from asthma. SO2 also reacts with other chemicals in the air to form tiny sulfate particles, contributing to levels of PM2.5.

    SO2 also reacts with other chemicals in the air to form acids, which fall to the earth as acid rain. Acid rain damages forests and crops, changes the makeup of soil, and makes lakes and streams acidic and unsuitable for fish.

    In the 1990 Clean Air Act Amendments, EPA implemented the Title IV cap-and-trade program to reduce emissions of SO2 and nitrogen ox

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