introduction to air and ventilation in the context of public health

2. Introduction to
air and
ventilation
PRESENTED BY:
DR.SANA MURTAZA

3. Air
 Air is the earth’s atmosphere. It is the clear gas in which living things live and
breath. It has an indefinite shape and volume. It has no colour and smell. It is a
matter as it has mass and weight. Air creates atmosphere pressure.

4. Composition of air
 Air is a mechanical mixture of gases.
 The normal composition of external air by volume is approximately as follows:
 Nitrogen 78.1%
 Oxygen 20.93%
 Carbon dioxide 0.03%
 The balance is made up of other gases which occur in traces eg, argon, neon,
krypton, xenon and helium

5. Impurities in air
 Air is rendered impure by:
 Respiration of men and animals.
 Combustion of coal, gas, oil etc.
 Decomposition of organic matter.
 Trade, traffic and manufacturing processes.

6.  Self cleansing mechanism which operate in
nature:
1-Wind: Wind dilutes and sweeps its impurities by its movement.
2-Sunlight: Oxidizing impurities and killing bacteria.
3- Rain: It cleanses the atmosphere by removing the suspended
and gaseous impurities.
4-Plant life: The green plants utilize the carbon dioxide and
generate oxygen.

7.  As a raindrop falls through the
atmosphere, it can attract tens to
hundreds of tiny aerosol particles to its
surface before hitting the ground. The
process by which droplets and aerosols
attract is coagulation, a natural
phenomenon that can act to clear the air
of pollutants like soot, sulfates, and
organic particles.

8. Chemical and physical changes in air:
Chemical changes:
 The air becomes progressively contaminated by carbon dioxide and the oxygen content
decrease due to metabolic process.
 An average person at rest gives off 0.7cft of carbondioxide per hour.
Physical changes:-
 1-rise in temperature.
 2-increase of humidity.
 3-decrease in air movement.
 4-Body odour
 5-bacterial pollution.

9. Discomfort:
 Discomfort is a subjective sensation which people experience in ill ventilated and crowded
rooms.
 It is now established that the causes of discomfort are not due to chemical change but
physical changes. These are
 Temperature.
 Humidity.
 Air movement.
 Heat radiation.

10. Comfort zone
 It is defined as the range of effective temperatures, over which majority of adult
feels comfortable.
 A temp as high as 155°C with low humidity for short period can be
tolerated;where as temp of 80-90 °F with high humidity for long periods can not
be tolerated

11. Air pollution
 The term is applied when there is an excessive concentration of foreign matter in
the outdoor atmosphere which is harmful to man or his environment.

12. Classification of air pollutant
 Primary pollutant:
Primary air pollutant are those that are emitted in
to the atmosphere from a source such as factory
chimney or exhaust pipe , or through suspension
of contaminated dusts by the wind.
 Secondary air pollutant:
Secondary air pollutant which are produced in the
atmosphere when certain chemical reactions take
place among primary pollutants

13. Sources of air
pollution
1-Automobiles.
2-industries.
3-Domestic sources.
4-Miscellaneous.

14. Air pollutants
Carbonmonooxide. Carbondioxide. Hydrogen sulphide. Sulphur dioxide.
Sulphur trioxide. Nitrogen oxides. Flourine compounds.
Organic compounds (e.g
hydrocarbons, aldehydes,
ketones , organic acids ).

15. Air pollutants
Metallic components e.g arsenic, zinc, iron).
Radioactive compounds.
Photochemical oxidants (e.g ozone).
Others include asbestos, beryllium, mercury, benzene,
fluoride, vinyl chloride, lead and radiation.

16. Ozone 03
 Ozone at ground level not to be confused with ozone layer in the upper
atmosphere.
 It is major constitute of photochemical smog.
 Photochemical smog is a mixture of pollutants that are formed when nitrogen
oxides and volatile organic compounds (VOCs) react to sunlight, creating a brown
haze above cities.
 The components of photochemical smog are ozone, nitric oxide, acrolein,
formaldehyde and peroxyacyl nitrate (PAN).
 Highest level of ozone pollution occur during period of sunny weather.

17. Example
 Ozone and nitric oxide (NO) can irritate the nose and throat and their high
concentration causes a headache, chest pain, dryness of the throat, cough and
difficulty in breathing.

18. Effects
 Breathing problem.
 Triggers asthma.
 Lung disease.
 Daily mortality rise by
0.3% and that for heart
disease by 0.4%

19. What is smog??

20. Indoor air
pollution

21. Hazards of household air pollution
 4.3 million people die every year prematurely from illness attributable to
household air pollution caused by inefficient use of solid fuels.
 Among these deaths 12% due to pneumonia.
 34%from stroke
 26% from ischemic heart disease.
 22% from COPD.
 6% from lung cancer.

22.  Over half of deaths among children less than 5 yrs old from acute lower
respiratory tract infection are due to partriculate matter inhaled from indoor air
pollution from household solid fuels.

23. Major air pollutants, their sources and
adverse effects
Noxious agent sources Adverse effects
Oxides of nitrogen Automobile, exhaust, gas stove
and heaters, wood burning
stoves, kerosene space heaters.
Respiratory tract irritation,
bronchial hyperactivity, impaired
lung defences, bronchiolitis
obliterans.
hydrocarbon Automobile exhaust, cigarette
smoking
Lung cancer
ozone Automobile exhaust, high
altitude aircraft cabins
Cough, substernal discomfort,
bronchoconstriction, respiratory
tract irritation.
Sulphur dioxide Power plant, smelters, oil
refineries, kerosene space
heaters.
Exacerbation of asthma, COPD,
respiratory tract irritation,
lead Automobile exhaust, leaded
gasoline.
Impaired neuropsychological
development in children

24. Prevention and control of air pollution
 1- Containment: That is, prevention of escape of toxin substances in to ambient
air.
 2-Replacement: replacing a technological process causing air pollution e.g solar
power generation, natural gas, reduce lead in petrol.
 3-Dilution: Establishment of green belts between industrial and residential areas
is an attempt at dilution.
 4- Legislation: Air pollution is controlled in many countries by suitable legislation
e.g: Clean air acts.

25.  E- International action: To deal with air pollution on a world wide scale , WHO
has established an international network of laboratories for the monitoring and
study of air pollution.

26. Disinfection of air
 1- Chemical ventilation.
 2-Ultravoilet radiation.
 3- Chemical mists.
 4- Dust control.

27. Ventilation
 The modern concept of ventilation implies not only the replacement of vitiated air
by a supply of fresh outdoor air, but also the quality of incoming air with regards
to its temperature, humidity and impurity with a view to provide thermal
environment that is comfortable and free from risk of infection.

28. Types of ventilation
 1-Natural ventilation.
 2-Mechanical ventilation.

29. Natural ventilation
 Natural ventilation is the simplest system of ventilating small dwellings, school
and offices.
 In this method reliance is placed on certain forces which operate in nature. These
are:
 The wind.
 Diffusion.
 Inequality of temperature.(air is flow from higher density to low density)

30. Wind
 Wind: The wind is an active force in ventilation .When it blows through a room it
is called perflation.
 When there is an obstruction, it bypasses and exerts a suction action at its tail end
, this is called aspiration.

31. Mechanical ventilation
 1- Exhaust ventilation.( in this system, air is extracted or exhausted to the outside
by exhaust fans usually driven by electricity.)
 2-Plenum ventilation.(in this system fresh air is blown in to the room by
centrifugal fans so as to create a positive pressure, and displace the vitiated air).
 3-Balanced ventilation.(this is combination of exhaust and plenum system of
ventilation)
 4- Air conditioning.