AIR

AIR

INTRODUCTION

Air is the invisible gaseous, substance surrounding the earth, a mixture mainly of oxygen and nitrogen. Air is a precious resource that most of us take for granted. Air supplies us with O₂, which is essential for our bodies to live. Without it, we would die within minutes. Pure air is a mixture of several gases that are invisible and odourless. It consists of about 78% nitrogen, 21% oxygen, and less than 1% of argon, carbon dioxide, and other gases — as well as varying amounts of water vapour. Adults breathe in about 10-20 cubic metres of air every day. That’s about 20,000 breaths. Children breathe almost twice that amount because they are smaller, and their respiratory systems are still maturing. 

The environment consists of four segments namely Biosphere, Lithosphere, Hydrosphere and Atmosphere.

Biosphere: The environment which supports life and sustains various human activities is known as biosphere. Word Biosphere is derived from Latin word, BIO, which means Life.

Lithosphere: It is the outer mantle of the solid earth i.e. earth crust consisting of rocks and soil. The soil is the most important part of lithosphere. Word lithosphere is derived from Latin word, LITHO, which means stone.

Hydrosphere: It includes all kinds of water resources, oceans, rivers, lakes, streams, glaciers, polar ice caps and ground water. Word Hydrosphere is derived from Latin word, HYDRO, which means Air.

Atmosphere: It is the protective blanket of gases surrounding the earth. The main components of the atmosphere are nitrogen (78%), oxygen (20.95%) and minor components are argon, hydrogen, ozone and other inert gases like helium and neon. Word Atmosphere is derived from Latin word, ATMO, which means Air.

Composition of Air

Air is invisible, colourless, odourless and tasteless. Air has mass and it exerts pressure. Air is not a single gas. It is a mixture of many gases, water vapour and other particulate matter. The actual composition of air varies from place to place.  Near the earth’s surface, air mainly consists of nitrogen and oxygen, carbon dioxide and water vapour. Of all the components of air, carbon dioxide (CO₂) has the highest solubility in water.

The actual average composition of the air near the earth’s surface (atmosphere) is given below in table: The percentage of almost all the gases except carbon dioxide, remain nearly constant. The proportions of carbon dioxide (CO₂), water vapour (H₂O) and dust/smoke particles in the air keep changing from time to time and place to place. For example, the air around an industrial area contains more carbon dioxide.

IMPORTANCE

Air is used to burn things, for example, a log. The oxygen in the air reacts with the stuff in the log to make a bunch of new stuff. The air we breathe in (this is important - if we don't breath, we die pretty quick) is used to burn the stuff we eat to make energy that we can use to eat more. The oxygen in the air pretty much drives our life. Plants use the carbon dioxide in the air to make sugars which they will later burn for energy. Air also suspends clouds, which are water and turn into rain. This means that water moves around a lot. If water just sat around, a lot of things could only grow in a river. Air also suspends objects. Think of it as swimming in water - just harder, so hard that it takes a bunch of smart people to figure out just how. Planes "float" on air. Air holds heat, too. If there was no air, night would be colder than that stuff the doctor uses to freeze off your warts. All that energy from the sun would just leave instead of being held in by the air. Air can also be a problem, it is hard for things to move around in it and it can push things. When you are walking around your living room this is not noticeable, but when you are driving a car really fast and watching that gas tank empty (or being impaled by flying debris in a hurricane) the "push" of air becomes a lot more noticeable.

·         Air also suspends clouds, which are water and turn into rain.

·         The air we breathe in (this is important - if we don't breath, we die pretty quick) is used to burn the stuff we eat to make energy that we can use to eat more. The oxygen in the air pretty much drives our life.

·         Plants use the carbon dioxide in the air to make sugars which they will later burn for energy.

·         Air also suspends objects.

·         Air holds heat, too.

·         Air maintain temperature

·         Due to the air movement, we can dry things & it can covert to electricity.

·         Air plays major role in chemical process

VENTILATION

Ventilation can be defined as the process of applying fresh air and removing contaminated air by natural or mechanical means to or from an enclosed area or any particular environment to provide excellent condition for working and living. Adequate ventilation is prime requirement but air movement, temperature, humidity conditions and purity of fresh air also equally important.

The rate of air change will depend upon the volume of the room. The changes of the air required as for the activity going on that premises, number of persons using premises etc. It will also depend on high velocity of fresh air quantity of heat, moisture and odour present in the room. The rate of air change should not be too frequent as it will result in discomfort due to high velocity of temperature and humidity.

Air conditioning: It can be defined as the simultaneous control of temperature humidity and air motion.

Industrial ventilation: Ventilation is the mechanical system in a building that brings in "fresh" outdoor air and removes the "contaminated" indoor air. In a workplace, ventilation is used to control exposure to airborne contaminants. It is commonly used to remove contaminants such as fumes, dusts, and vapours, in order to provide a healthy and safe working environment. Ventilation can be accomplished by natural means (e.g., opening a window) or mechanical means (e.g., fans or blowers). Industrial systems are designed to move a specific amount of air at a specific speed (velocity), which results in the removal (or "exhaust") of undesirable contaminants. While all ventilation systems follow the same basic principles, each system is designed specifically to match to the type of work and the rate of contaminant release at that workplace.

There are four purposes of ventilation: 

1.      Provide a continuous supply of fresh outside air.

2.      Maintain temperature and humidity at comfortable levels.

3.      Reduce potential fire or explosion hazards.

4.      Remove or dilute airborne contaminants.

Necessity of ventilation

• To create air movement.
• To prevent an undue accumulation of CO₂ and moisture.
• To prevent depletion of O₂ content in air.
• To prevent flammable concentration of gas vapour and dust.
• To prevent undue concentration of body odours, Fumes, dust and other industrial products.
• To prevent undue concentration of bacteria carrying particles.
• To prevent condensation in the building.
• To remove body heat liberated by other equipment. When heat gain or solar radiation is excessive, then air –conditioning should be considered.
• To prevent suffocating conditions in halls, cinema halls and other such building where mass assembly is of the regular feature.
• To admit fresh air and push out contaminated air.

Factors affecting ventilation

• Rate of fresh air change.
• Control on humidity.
• Quality of air.
• Temperature.
• Use of the building.

Saturated air: When a specific volume of air at a specify temperature holds as much water vapour as it can. It is said to be saturated air at that temperature.

Relative humidity: The relative humidity of the air is the amount of water that is present in the air compared to the greatest amount it would be possible for the air to hold at that temperature: If relative humidity is more or less than the desired value at specific temperature, It causes discomfort to the occupants for eq. at 21°C range of 30° to 70°C relative humidity is considered desirable.

Essentials of a good ventilating system

1)      It should admit required amount of fresh air in the room.

2)      It should effectively extract the contaminated air in the room.

3)      All the corners of the room should get proper ventilation.

4)      The value of the desired relative humidity should be maintained.

5)      Effective temperature should be maintained with regard to human comfort.

6)      It should exercise full control or incoming air and extracted air.

7)      The ventilating air should be free from impurity like dust odour etc.

TYPES OF VENTILATION

 Mechanical or forced ventilation: through an air handling unit or direct injection to a space by a fan. A local exhaust fan can enhance infiltration or natural ventilation, thus increasing the ventilation air flow rate.

Natural ventilation occurs when the air in a space is changed with outdoor air without the use of mechanical systems, such as a fan. Most often natural ventilation is assured through operable windows but it can also be achieved through temperature and pressure differences between spaces. Open windows or vents are not a good choice for ventilating a basement or other below ground structure. Allowing outside air into a cooler below ground space will cause problems with humidity and condensation.

Mixed Mode Ventilation or Hybrid ventilation: utilises both mechanical and natural ventilation processes. The mechanical and natural components may be used in conjunction with each other or separately at different times of day. The natural component, sometimes subject to unpredictable external weather conditions may not always be adequate to ventilate the desired space. The mechanical component is then used to increase the overall ventilation rate so that the desired internal conditions are met. Alternatively the mechanical component may be used as a control measure to regulate the natural ventilation process, for example, to restrict the air change rate during periods of high wind speeds.

Infiltration is separate from ventilation, but is often used to provide ventilation air.

Infiltration is the unintentional or accidental introduction of outside air into a building, typically through cracks in the building envelope and through use of doors for passage. Infiltration is sometimes called air leakage. The leakage of room air out of a building, intentionally or not, is called exfiltration. Infiltration is caused by wind, negative pressurization of the building, and by air buoyancy forces known commonly as the stack effect.

SYSTEM OF VENTILATION

There are two systems of ventilation Natural ventilation and Mechanical or artificial ventilation.

1.         Natural ventilation

Natural system of ventilation is considered suitable for small houses and not for big buildings like assembly hall, theatre, Auditorium and large factory, workshops. The systems of ventilation largely depend upon the scientific location of doors, windows, ventilation etc. The wind is supply inside the building, doors, windows and other opening. The wind enters the room and gets heated of and lifted of induce cores of time. Heated air is driven out through ventilation provided near ceiling. An opening area equal to not less than 1/20th of the floor area of the room should be provided for proper ventilation. The top of this opening area should be not more than 45cm bellow the ceiling. The rate of ventilation by natural means depends upon two effects and principals. First principal is depends on wind effect or wind actions upon the

a.       Wind effect or wind action

b.      Stack effect

Wind effect or wind action: Ventilation by wind effect is affected by the direction and velocity of outside wind and sizes and positions of the openings. Wind create pressure difference and when it blows against a building causes a positive pressure on the wind ward side and suction on the lee ward side. This pressure difference causes wind to blow through the building and causes air change if proper opening are provided. This action is known as wind effect or wind action.

Stack effect: Fresh admitted air inside the building is cool and heavy. This become hot after some time and is lifted up. Lifted up air is escaped through ventilators or openings in the roof. Fresh again comes in the building gets lifted up by heating and again escape through opening provided near the ceiling. This effect cause flow is the wind in upward direction and is known as stack effect.

2. Mechanical system of ventilation

The system of ventilation in which some mechanical arrangement are make to provide adequate ventilation in the room is called as mechanical system of ventilation. It is costly method but it result in considerable increase in the efficiency of the person working under such condition. This system is applicable for big offices, bank, theatres, auditoriums and industrial plants. Mechanical ventilation is broadly classified into 4 types.

a.      Extract or exhaust system: In this system, partial vacuum is developed inside the room by extracting contaminated air by fixing fans or blowers at the outlets. The pressure inside being low, the fresh air from outside force in through doors and windows and through available opening. In this system continuous fresh air flow inside the room can be maintained.

b.      Supply or Plenum system: This system is reverse of exhaust system. Fresh air is poured with the help of input fans or blowers into the room and polluted air allowed to leave the room by it-self. In this case pressure inside the room is greater than that of the atmospheric and as such all leakage of air is outwards. Mostly this system is use in Bakery.

c.       Balancing system: This system use it supply fan to supply and to extract air. It enables full control over air movement and conditions to be obtain, and should be used where accurate performance is required. Recirculation of air is possible in this system.

d.      Air Condition: The process of creating, controlling and maintaining indoor atmospheric condition suited to requirement for man or to the needs of thing is called A.C. This process consist of conditioning of air with respect to humidity, temperature, odour, bacteria content, dust content and air movement and so that comfortable condition are maintained inside the room.

Packaged air condition: Window air cooled packaged units are available up to a limited capacity. Floor mounted self-contained packaged units are made to meet the requirements for large capacity. This unit comprises a compressor, condenser, evaporator, fans, filters and controls. It may also include means for heating, humidifying or ventilating air. This units are a designed for application is residences and in the smaller commercial market, shops, restaurants, small office units etc. The package unit can be mounted within air conditions space or remote in a separate enclosure commercial packaged air conditioners are available in sizes of normal cooling capacity 10,000W and above.

Temperature control

*  Temperature range which is liked by majority of people is called comfortable zone.

*  The comfortable zones are different for winter and summer due to the changes in the body temperature.

*  Effective temperature zones for summer and winter range between 20 to 23°C and 18 to 22°C respectably.

*  The temperature of 21°C to 22.5°C is regarded as most likely comfort temperature in a room. Regardless of outside temperature.

AIR POLLUTION

Air pollution is the introduction into the atmosphere of chemicals, particulates, or biological materials that cause discomfort, disease, or death to humans, damage other living organisms such as food crops, or damage the natural environment or built environment. The atmosphere is a complex dynamic natural gaseous system that is essential to support life on planet Earth. Stratospheric ozone depletion due to air pollution has long been recognized as a threat to human health as well as to the Earth's ecosystems. There are two types of pollutants: Primary pollutants are those gases or particles that are pumped into the air to make it unclean. They include carbon monoxide from automobile exhausts and sulphur dioxide from the combustion of coal. Secondary pollutants: When pollutants in the air mix up in a chemical reaction, they form an even more dangerous chemical. Photochemical smog is an example of this, and is a secondary pollutant.

Air pollutants consist of gaseous pollutants, odours, and SPM, (suspended particulate matter) such as dust, fumes, mist, and smoke. The concentration of these in and near the urban areas causes severe pollution to the surroundings. The largest sources of human-created air pollution are energy generation, transportation, and industries that use a great deal of energy sources. Depending on their source and interactions with other components of the air, they can have different chemical compositions and health impacts. Since these pollutants are generally concentrated in and around urban areas, the outdoor urban pollution levels are far higher than in the rural areas.

Fires are another major source of air pollution and can lead to severe problems if the smoke is inhaled for a period of time. These fires can either be forest fires, oil well fires, burning of leaves in the backyard or as in the case of rural areas, large-scale burning of agricultural waste. Other sources include industries and power plants located in these areas. Some of the common pollutants and there effects on health are:

Indoor air pollution

Cooking and heating with solid fuels on open fires or traditional stoves results in high levels of indoor air pollution. Indoor smoke contains a range of health-damaging pollutants, such as small particles and carbon monoxide. Indoor cooking and heating with biomass fuels (agricultural residues, dung, straw, wood) or coal produces high levels of indoor smoke that contains a variety of health-damaging pollutants. There is consistent evidence that exposure to indoor air pollution can lead to acute lower respiratory infections in children under five, and chronic obstructive pulmonary disease and lung cancer (where coal is used) in adults.

PREVENTION OF AIR POLLUTION:

Solution efforts on pollution are always a big problem. This is why prevention interventions are always a better way of controlling air pollution. These prevention methods can either come from government (laws) or by individual actions. In many big cities, monitoring equipment has been installed at many points in the city. Air pollution can be avoided by using simple practices like:

*        Using smokeless sources of energy like smokeless stoves, which use biogas, solar energy, etc.

*        Using devices for filtering smoke in chimneys of factories and powerhouses.

*        Planting more trees.

*        Locating industries away from residential areas.

*        Strictly checking pollution levels in automobiles’ exhaust emission.

*        Bifurcate smoking and non-smoking areas of hotel.

*        Smoking zones should be there in open air and it should be denoted as smoking zone.

*        Encourage the guest to not smoke in non-smoking areas, rooms, public areas etc.

*        The smoking zone should be nearby Bar to assist drunken guest for smoking.

A “green” lodging property is a property that is managed to be environmentally-friendly, by making a conscious effort to reduce pollution. Many people prefer to stay at a hotel that follows “green” principles; this may result in increased income. Being a “green” hotel, which includes improving air quality, tells the world that the environment is important to you. Being a “green” hotel also raises the awareness of both your staff and guests about the need to be as environmentally-friendly as possible. When your guests learn about a hotel’s environmental activities, they provide positive feedback, indicating increased customer satisfaction.

Health effects of CFCs

Chlorofluorocarbons (CFCs) are organic compounds, and contain carbon, fluorine and chlorine atoms. The most notable effect of CFCs on the environment is the depletion of the ozone layer. The ozone layer is essential to most life on Earth, as it shields life forms from a large portion of the UV (ultraviolet) rays from the sun. Depletion of the ozone layer can lead to various problems for humans and other life forms on Earth, which lead to strong regulation, imposed on CFCs. CFCs damage the ozone layer. One example of the consequences of CFCs is the ozone layer hole right above the South Pole. There is evidence to suggest that CFCs, or chlorofluorocarbons, deplete the ozone layer. The problem with this is that with the depletion of the ozone layer comes a loss of protection from harmful UV radiation from the sun. For example, in New Zealand where the air is purest and the ozone layer thinner, rates of skin cancer are among the highest in the world. Since the appearance of an ozone hole over the Antarctic in the early 1980s, Americans have become aware of the health threats posed by ozone depletion, which decreases our atmosphere's natural protection from the sun's harmful ultra-violet (UV) rays. Eye Damage, Immune Suppression Skin Cancer etc. are most common disease due to CFC.

SUMMARY

The only reason Earth can sustain life is because of its atmosphere, which keeps air readily available for chemical reactions. A number of different gases, including oxygen, make up the Earth's atmosphere in a mixture that keeps plants, animals and people alive. In addition to sustaining life, air plays a role in many other important functions that are best performed when air quality is high.

Since the onset of the industrial revolution, there has been a steady change in the composition of the atmosphere mainly due to the combustion of fossil fuels used for the generation of energy and transportation. Hotels can be blamed to produce more pollution as compare to other industry and sector. Lodging properties can produce toxic air pollutants and ozone-depleting substances. Cleaning supplies, synthetic materials, paints, and pesticides can release toxic air pollutants and volatile organic compounds (VOC). Although emitted indoors, these air pollutants will also eventually leak into the outdoor air through doors, ventilation systems, and other

Air pollution is contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere. Household combustion devices, motor vehicles, industrial facilities and forest fires are common sources of air pollution. Pollutants of major public health concern include particulate matter, carbon monoxide, ozone, nitrogen dioxide and sulphur dioxide. Outdoor and indoor air pollution cause respiratory and other diseases, which can be fatal. Air is mainly composed of nitrogen, oxygen, and argon, which together constitute the major gases of the atmosphere. The remaining gases are often referred to as trace gases, among which are the greenhouse gases such as water vapour, carbon dioxide, methane, nitrous oxide, and ozone. Filtered air includes trace amounts of many other chemical compounds. Many natural substances may be present in tiny amounts in an unfiltered air sample, including dust, pollen and spores, sea spray, and volcanic ash. Various industrial pollutants also may be present, such as chlorine (elementary or in compounds), fluorine compounds, elemental mercury, and sulphur compounds such as sulphur dioxide [SO₂]. Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapour, on average around 1%.

Recycle and re-use things. This will minimize the dependence of producing new things. Remember manufacturing industries create a lot of pollution, so if we can re-use things like shopping plastic bags, clothing, paper and bottles, it can help.

FACTS

ü  CNG  (Compressed natural gas)  is a clean fuel

ü  DDT causes excessive growth of algae in water bodies.

ü  Ozone hole is largest over Antarctica.

ü  Carbon monoxide is a pollutant because it Causes burning of eyes

DEFINITIONS FOR TERMS

1.      SPM: suspended particulate matter

2.      Ventilation rate: the amount of outdoor air that is provided into the space, and the quality of the outdoor air.

3.      Acid Rain: Rain that is especially acidic (pH is less than 5.2). Principal components of acid rain typically include nitric and sulphuric acid. These may be formed by the combination of nitrogen and sulphur oxides with water vapour in the atmosphere.

4.      Air Pollution: Degradation of air quality resulting from unwanted chemicals or other materials occurring in the air.

5.      Air Pollutants: Amounts of foreign and/or natural substances occurring in the atmosphere that may result in adverse effects to humans, animals, vegetation and/or materials.

6.      Catalyst: A substance that can increase or decrease the rate of a chemical reaction between the other chemical species without being consumed in the process.

7.      Volatile organic compounds (VOCs) -- Organic chemicals all contain the element carbon (C). Organic chemicals are the basic chemicals found in living things and in products derived from living things, such as coal, petroleum, and refined petroleum products. Many of the organic chemicals we use do not occur in nature, but were synthesized by chemists in laboratories. Volatile chemicals readily produce vapours at room temperature and normal atmospheric pressure. Vapours escape easily from volatile liquid chemicals. Volatile organic chemicals include gasoline, industrial chemicals such as benzene, solvents such as toluene and xylene, and tetrachloroethylene (perchloroethylene, the principal dry cleaning solvent). Many volatile organic chemicals, such as benzene, are also hazardous air pollutants.

8.      Zero Air -- Pure air, used for calibrating air monitoring instruments. The EPA requires zero air to have less than 0.1 ppm of hydrocarbons.

9.      Sulphur dioxide -- A criteria air pollutant. Sulphur dioxide is a gas produced by burning coal, most notably in power plants. Some industrial processes, such as production of paper and smelting of metals, produce sulphur dioxide. Sulphur dioxide is closely related to sulphuric acid, a strong acid. Sulphurs dioxide plays an important role in the production of acid rain.

10.  Ozone depletion -- The reduction in the stratospheric ozone layer. Stratospheric ozone shields the Earth from ultraviolet radiation. The breakdown of certain chlorine and/or bromine-containing compounds that catalytically destroy ozone molecules in the stratosphere can cause a reduction in the ozone layer.

11.  Cyclone: An air pollution control device that removes larger particles -- generally greater than one micron -- from an air stream through centrifugal force.

12.  Combined Heat and Power (CHP): An approach to generating power and thermal energy from a single fuel source. CHP application involves the recovery of otherwise wasted thermal energy to produce additional power or useful thermal energy.

13.  Asthma: a medical condition characterized by abnormal restriction of breathing, especially in response to allergens or air contaminants.

14.  Greenhouse Effect: the warming of the earth's atmosphere caused by a build-up of carbon dioxide and other trace gases. This build-up allows light from the sun's rays to heat the earth but prevents a counterbalancing loss of heat

15.  Global Warming: An increase in the temperature of the Earth's troposphere. Global warming has occurred in the past as a result of natural influences, but the term is most often used to refer to the warming predicted by computer models to occur as a result of increased emissions of greenhouse gases.

16.  Greenhouse Gas: A gas, such as carbon dioxide or methane, which contributes to potential climate change.

17.  Smog is a type of air pollution; the word "smog" was made in the early 20th century as a portmanteau of the words smoke and fog to refer to smoky fog.

References: Principles of Food Sanitation (Fifth Edition) Norman G. Marriottand Robert B. Gravani, food sanitation (Rufus K. Guthrie http://labspace.open.ac.uk/course/view.php?id=6724

                                         

TEST YOURSELF

Fill in the blanks

1.      The environment consists of _________ segments.

2.      Atmosphere consists of about ___________ nitrogen.

3.      Atmosphere consists of about ___________ oxygen.

4.      Stack effect is due to ___________ type of ventilation

5.      Word Atmosphere is derived from _________ word, ATMO, which means Air.

6.      Word Biosphere is derived from _________ word BIO, which means _________.

7.      Word CHP stands for ___________.

8.      The only reason Earth can sustain life is because of its ________________.

9.      Smog is mixture of _________ and _________.

10.  Carbon monoxide is a pollutant because it Causes _____________.

11.  Refrigerators and air conditioners have _________ gas.

12.  Acid rains are due to __________________.

13.  Use of excessive fertilizer in fields leads to the deficiency of _______in the nearby water body.

14.  CNG stands for ______________.

Answer the Questions:

1.      What is air pollution? Describe common pollutant.

2.      Write a brief description of components of air.

3.      Write importance and function of air.

4.      What is ventilation? Describe types of ventilation.

5.      Explain how CFC is harmful for health.

6.      What are the environmental effects of pollutant gases?

7.      What is stack effect?

ANSWER KEYS

Fill in the blanks

1.      4

2.      78%

3.      21%

4.      Mechanical or artificial

5.      Natural

6.      Latin

7.      Latin , Life

8.      Combined Heat and Power

9.      Atmosphere

10.  smoke and fog

11.  Burning of eyes

12.  Chlorofluorocarbons

13.  Oxides of sulphur

14.  Oxygen

15.  Compressed natural gas