hvac

1. BMCT 4153
Faculty of Mechanical Engineering, UTeM,
Semester 1, 2012/2012
By Fadhilah binti Shikh Anuar

2. 1. Introduction – Malaysia and Energy Policy
2. Introduction to Heating, Ventilating and Air
Conditioning (HVAC)
3. Classification of HVAC System
4. Application of HVAC
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3.  At the end of this lecture, the students should be
able to:
 Define air conditioning and refrigeration system.
 Discuss in depth the air conditioning and refrigeration
types and applications used in everyday life.
 Discuss terms associated with the refrigeration system
and air conditioning performance.
 Describe the fundamental underlying scientific principles
and theory of refrigeration system and air conditioning.
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4.  Population: 26,896,751 (December 2006 est.) – now estimated 28 million plus
 Geographic coordinates: 2 30 N, 112 30 E
 Area: total: 329,750 sq km, land: 328,550 sq km, water: 1,200 sq km
 Climate: tropical; annual southwest (April to October) and northeast (October to
February) monsoons
 Natural resources: petroleum, timber,, copper, iron ore, natural gas, tin bauxite
 Environment - international agreements:
Biodiversity, Climate Change, Climate Change-Kyoto Protocol, Desertification,
Endangered Species, Hazardous Wastes, Law of the Sea, Marine Life Conservation,
Ozone Layer Protection, Ship Pollution, Tropical Timber 83, Tropical Timber 94, Wetlands
 Export: electronic equipment, petroleum and liquefied natural gas, wood and wood
products, palm oil, rubber, textiles, chemicals
 Import: electronics, machinery, petroleum products, plastics, vehicles, iron and steel
products, chemicals
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5. OBJECTIVES
Three principal energy objectives are instrumental in guiding the future energy sector
development. They are:-
1. The Supply Objective (Objektif Pembekalan)
To ensure the provision of adequate, secure and cost-effective energy supplies
through developing indigenous energy resources both non-renewable and
renewable energy resources using the latest cost options and diversification of
supply sources both from within and outside the country;
2. The Utilization Objective (Objektif Penggunaan)
To promote the efficient utilization of energy and discourage wasteful and non-
productive patterns of energy consumption; and
3. The Environmental Objective (Objektif Persekitaran)
To minimize the negative impacts of energy production, transportation, conversion,
utilization and consumption on the environment.
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6. Secure supply
•Diversification of fuel type and sources, technology, maximize use of
indigenous energy resources, adequate reserve capacity to cater for
contingencies [adequate reserve margin for generation, upgrading
transmission and distribution networks and distributed generation
(islanding);
Sufficient supply
•Forecast demand, right energy pricing and formulate plans to meet
demand.
Efficient supply
•Promote competition in the electricity supply industry.
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7. Cost-effective supply
•Promote competition and provide indicative supply plan to meet
demand based on least cost approach using power computer
software such as WASP;
Sustainable supply
•Promote the development of renewable and co-generation as
much as possible.
Quality supply (low harmonics, no surges and spikes, minimal
variation in voltage)
•Match quality with customer demand with variable tariffs
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8.  Efficient utilization of energy
• Bench marking, auditing, financial and fiscal
incentives, technology development, promotion of
ESCOs, Labelling, Ratings, correct pricing, energy
managers; and
 Minimizing Negative Environmental Impacts
• Monitor the impacts, improve efficiency of utilization
and conversion and promote renewable.
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9. • Centre for Education and Training for Renewable Energy and Energy Efficiency(CETREE)
• Project on Capacity Building in Integrated Resources Planning (IRP) at Government and
Related Agencies
• MECM's Low Energy Office (LEO) Project at Putrajaya
• Small Renewable Energy Programme (SREP)
• Demand Side Management (DSM) Project
• Green Building Index
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10.  Coefficient of Performance (COP)
A ratio calculated by dividing the total heating capacity provided by the
heat pump, including circulating fan heat but excluding supplementary
resistance heat (Btus per hour), by the total electrical input (watts) x
3.412.
 Energy Efficiency Ratio (EER)
A ratio calculated by dividing the cooling capacity in Btus per hour (Btu/h)
by the power input in watts at a given set of rating conditions, expressed
in Btu/h per watt.
 Seasonal Energy Efficiency Ratio (SEER)
SEER is a measure of cooling efficiency for air conditioning products. The
higher the SEER rating number, the more energy efficient the unit is.
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11.  SEER – The Seasonal Energy Efficiency Ratio is a representation of the cooling
season efficiency of a heat pump or air conditioner in cooler climates. It applies
to units of less than 65,000 Btuh capacity
 EER – The Energy Efficiency Ratio is a measure of a unit’s efficiency at full load
conditions and 95 degrees outdoor temperatures. It typically applies to larger
unit over 65,000 Btuh capacity.
 HSPF – The Heating Season Performance Factor is a representation of the
heating efficiency of a heat pump in cooler climates.
 COP – Coefficient of Performance is the measure of heating efficiency of a heat
pump at a constant temperature of 47 degrees.
 Btuh – Btuh or Btu/h is a rate of heating or cooling expressed in terms of British
Thermal Units per Hour.
 Ton – One ton of cooling is the energy required to melt one ton of ice in one
hour. One ton = 12,000 Btuh
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12. Heating, ventilation & Air conditioning (HVAC) is the technology
of indoor and automotive environmental comfort.
HVAC system design is a major sub discipline of mechanical
engineering, based on the principles of thermodynamics,
fluid mechanics, and heat transfer.
Refrigeration is sometimes added to the field’s abbreviation as
HVAC & R or HVACR.
HVAC is important in the design of medium to large industrial
and office buildings where safe and healthy building
conditions are regulated with respects to temperature and
humidity, using fresh air from outdoors.

13.  It refers to the control of temperature, moisture content, cleanliness, air
quality, and air circulation as required by occupants, a process or a
product in the space. ~ by Willis Carrier
 Based on ASHRAE (American Society of Heating, Refrigerating, and Air-
Conditioning Engineers) standard, indoor comfort conditions that are
thermally acceptable to 80% or more of a commercial building’s
occupants.
 Generally, these comfort conditions are called as the “comfort zones” –
temperature between 68 – 75 deg F for winter and 73-78 deg F during
summer. Room air relative humidity is 50% and moving at a slow speed
(velocity) of 30 feet/min or less.
 Acceptable range; temp: 70 to 75 deg F, relative humidity: 40 to 50%

14. It has many definition. Generally, as any process of
heat removal. It is also defined as that branch of
science which deals with the process of reducing
and maintaining, the TEMPERATURE space or
material below the temp. of the surroundings.
Therefore, the heat must be removed from the
body. The heat is transferred to another whose
temperature is below that of the refrigerated body.

15. Air conditioning Refrigeration
Heating, humidifying, Cooling & Industrial refrigeration,
and control of air dehumidifying including food
quality operations in air preservation, chemical
conditioning and process industries

16. In any refrigerating process, the body used as the
heat absorber or cooling agent is known as
Refrigerant.  another sub topic in this subject
 According to the effect of heat absorbed by the
refrigerant, all cooling processes may be classified
as either SENSIBLE or LATENT.
 Sensible process – when the absorbed heat cause
an increase in the TEMPERATURE of refrigerant
 Latent process – when the absorbed heat cause a
change in physical state of the refrigerant.

17.  Unit in HVAC, include both; English and SI units.
Examples:
 gpm (gallons per minute) for liquid volume flow rates
 cfm (cubic feet per minute) for air volume flow rates
 in.wg (inches water gauge) for pressure
measurement in air-flow systems
 ton (12,000 Btu per hour) for the description of
cooling capacity or rate
 ton-hr (12,000 Btu) for cooling energy

18. 1. Provide the cooling and heating energy as required
2. Condition (process) the supply air by:
(a) heat or cool,
(b) humidify or dehumidify,
(c) clean and purify, and
(d) attenuate any objectionable noise produced by
the HVAC&R equipment
3. Distribute the conditioned air, containing sufficient outdoor
air, to the conditioned space.
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19. 4. Control and maintain the indoor environmental parameters
within predetermined limits between the conditioned space and
surroundings, which include:
a) temperature,
b) humidity,
c) cleanliness,
d) air movement,
e) sound level, and
f) pressure differential.
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20.  Power is the rate at which energy is produced or
consumed. With all other factors being equal,
the electrical power (kW) required by an HVAC
system or component depend on size.
 Size = capacity = load = demand
 The energy (kW-hr) used by an HVAC system
depends not only on the size, but also the on the
fraction of capacity or load at which the
operating and the amount of time that it runs.

21.  Determine the July electric utility bill for a facility
that used 112,000 kw-hrs during that month and
which had maximum power usage of 500 kw
during the peak periods of time in that month.
The utility has a fixed ‘meters’ charge of $75 per
month and charges of flat rate of 5 cents per kw-hr
for energy and $12 per kw for maximum power
usage during peak periods in July.

22.  The monthly bill is made up of a fixed meter
charge, a charge for energy, and a charge for peak
demand.
Fixed monthly meter charge =$75.00
Energy charge (112,000 kw-hrs x 0.05$/kw-hr)
= $5600.00
Demand charge (500 kw x $12.00/kw) = $6000.00
TOTAL monthly electric bill = $ 11,675.00

23.  Heat naturally flows from a higher energy
level to a lower energy level. In other words,
heat travels from a warmer substance to a
cooler substance.
 When there are temperature difference, heat
transfer will occur.
 The greater the temperature difference, the
greater the heat transfer

24. Three types of heat transfer:- conduction, convection, radiation.
 1 - Conduction (solid body with another solid body )
 Heat energy traveling from one molecule to another. Example: heat exchanger, home
furnace
 Different transfer rate, depends on the material/ solid body types.
 2 - Convection (solid body with flowing medium)
 when some substance that is readily movable such as air, water, steam ,refrigerant moves
heat from one location to another.
 HVAC system uses convection in the form of air, steam ,water, refrigerants in ducts and
piping to convey heat energy to various parts of the system.
 Natural convection – when air is heated, it rises
 Forced convection – when a fan or pump is used to convey heat in fluids such as air and
water.
 3 – Radiation (solid body with another solid body, have space between them )
 Heat transferred by radiation travels through space without heating the space.
 Example: The space heater does not heat the air (the space) but heats the solid objects that
come into contact with the heat rays.

25.  The heat content of a substance = enthalpy, h
 Unit enthalpy: Btu/lb or Btu/lb deg F
 Specific heat (Fahrenheit scale) is the amount of
heat necessary to raise the temperature of 1 lb of
a substance of 1 deg F
 Example:
 specific heat of water is 1 Btu/lb deg F
 specific heat of air is 0.24 Btu/lb deg F

26.  SENSIBLE HEAT
 Sensible heat is heat from people, lights, motors, heating
equipments, and outdoor air.
 E.g. A seated person in an office gives off approximately
225 Btuh of sensible heat into the conditioned space.
 Enthalpy units of sensible heat are in Btu/lb deg F.
 The change in the sensible heat level as measured with
ORDINARY THERMOMETER is sensible temperature.
 Sensible temperature is measured in degrees Fahrenheit
and it is indicated as dry bulb (db) temperature.

27.  LATENT HEAT
 Latent heat (hidden heat) is ; heat that is known to be added
to or removed from substance but no temperature change is
recorded.
 E.g. Heat released by boiling water
(involve physical change only; from liquid  vapour)
Once water is brought to the boiling point, adding more heat
only makes it boil faster, it does not raise the temperature of
water.
 Enthalpy units of latent heat are in Btu/lb deg F.
 Level of latent heat is measure in deg Fahrenheit and it is
indicated as dew point (dp) temperature.

28.  TOTAL HEAT
 Total heat = Sensible heat + Latent Heat
 Measure in deg F and it is indicated as wet bulb (wb)
temperature.
 Total heat level is measured with an ordinary
thermometer but the thermometer tip is covered with a
sock made from water-absorbing material.
 Enthalpy is in Btu/lb deg F.
 A seated person gives off approximately 450 Btuh of total
heat (225 Btuh sensible heat + 225 Btuh latent heat).

29. The rate of at which heat must be removed from
the refrigerated space or material in order to
produce or maintain the desired temp.
The heat load is the SUM of..
(a) Heat leaks through walls, doors, and window
(b) Heat that must be removed from the refrigerated
product
(c) Heat that must be removed from the people
working in space, by electric lights etc.

30.  In MKS*, the unit of refrigeration used is ton. In SI , system , kW is used as the unit of
refrigeration.
 Definition of the capacity of the system.
It is the rate at which it will remove heat from the refrigerated space, usually stated in kJ/hr
on in terms of its ice melting equivalent.
 Before the era of mechanical refrigeration, ice was widely used as a cooling medium.
Now, the cooling capacity of the mechanical refrigeration is compared with ice- melting
equivalent.
 When one-ton ice melts in one day, it will absorb,
900 x 335 = 30, 1500 kJ/day
where 900kg = 1 short ton, 335 kJ/kg = Latent heat of ice.
Heat absorbed/hr = 30, 1500/24 kJ/hr
Heat absorbed/sec = 30, 1500 / (24 x 3600) kJ/sec = 3.5 kJ/sec = 3.5 kW
*MKS is the system of units based on measuring lengths in meters, mass in kilograms, and
time in seconds.

31.  So, a mechanical refrigerating system having
the capacity of absorbing heat from the
refrigerated space at the rate of 3.5kW is
cooling at a rate equivalent to the melting of
1 ton ice in 24 hr and is said to have a
capacity of 1 ton.
 = 1 ton refrigeration (1TR)
 1 Ton = 3.5kJ/sec = 3.5 kW = 210 kJ/min =
12,600 kJ/hr

32.  Zeroth – standard measurement,
 Ta=Tb, Ta=Tc, then Ta=Tc
 First – energy balance (quantity)
 Energy In = Energy Out
 Second – energy quality, ds=dQ/T
 Third – Absolute zero
 Zero Kelvin
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33.  Basic properties
 Pressure, p
 Temperature, T
 Specific volume, v
 Specific Enthalpy, h
 Specific Entropy, s
 Specific Internal energy, u
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34.  p-v gives work, W
 T-s gives Heat, Q
 h-s, extensively used in steam generation processes
 p-h (Mollier diagram), used extensively in
refrigeration system
 Psychrometric chart (inverse of p-h diagram), used
extensively in Air Conditioning system
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35. 35

36. 36

37. 1. Performance requirements:
-on comfort, noise, control options, flexibility and meeting requirements of local
regulations/codes
2. Capacity requirements
-range of capacity, multiple units, zoning, etc.
3. Spatial requirement
-plant room space, space for ducting and piping (vertical shafts), space for
terminal equipment
4. Costs
-initial cost, operating cost and maintenance cost
5. Energy consumption
-for both economic and environment reasons
6. System qualities
-aesthetics, life, reliability and maintainability
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38. HVAC SYSTEMS
Central chilled Direct Expansion
Water AC system System
Window unit
All air Air-water All water
system Unitary & rooftop
system system
Split type & package
Single zone Induction Heat pump
Fan coil unit
Reheat Fan coil Central chilled water
VAV Two-pipe Water cooling tower
Dual duct Three-pipe
Multizone
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39. 1. Individual Systems : a self-contained , factory-made air
conditioner to serve one or two rooms (e.g. room/ window air
conditioner and split-type units). (Direct expansion system)
2. Unitary Packaged Systems: similar in nature to individual systems
but serve more rooms or even more than one floor, have an air
system consisting of fans, coils, filters, ductwork and outlets (e.g.
in small restaurants, small shops and small cold storage rooms).
3. Central (Hydronic) Systems: basically consists of three major
parts: (Central chilled water AC system)
a. Air system – air handling units (AHU), air distribution (air duct) system and
terminals.
b. Water system – chilled water system, hot water system, condenser water
system.
c. Central plant – refrigeration (chiller) plant, boiler plant. 39

41. 1. Window-mounted and floor - mounted units.
2. Split type conditioner
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42. 42

43.  In the split system, the indoor air handler comprises
controls and the air system, containing mainly:
a. fans,
b. filters, and
c. DX coils.
 The outdoor condensing unit is the refrigeration
system, composed of
a. compressors and
b. condensers.
 Rooftop packaged systems are most widely used.
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44. 44

46.  In larger buildings and particularly in multi-story
buildings, the split-system approach begins to run into
problems.
 1. running the pipe between the condenser and the air
handler exceeds distance limitations (runs that are too long
start to cause lubrication difficulties in the compressor)
 2.amount of duct work and the length of ducts becomes
unmanageable.
 Hence, chilled-water system is introduced.
 However need to use ‘cooling tower’
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49.  Used to dissipate the heat from the outside coil, hence
improved systems efficiency
 Cooling tower creates a stream of lower-temperature
water.
 Water runs through a heat exchanger and cools the hot
coils of the air conditioner unit.
 Costs more to buy the system initially, but the energy
savings can be significant over time (especially in areas
with low humidity): pay back time is fairly short (6-12
months).
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51.  Central (hydronic) air conditioning system consists
of:
a) an air system,
b) a water system,
c) a central heating /cooling plant, and
d) a control system.
Note: HVAC water-distribution systems = Hydronic system 51

52.  An air system is sometimes called the air-handling system.
 An air system function is to:
• Condition
• Transport
• distribute the conditioned,
• Recirculating outdoor, and exhaust air and
• Control the indoor environment according to requirements.
 Major components of an air system are:
1. air-handling units (AHU)
2. supply/return ductwork
3. fan-powered boxes
4. space diffusion devices and
5. exhaust systems.
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53.  An AHU usually consists of:
1. supply fan(s),
2. filter(s),
3. a cooling coil,
4. a heating coil,
5. a mixing box, and other accessories.
 An AHU conditions the outdoor/ recirculating air, supplies the
conditioned air to the conditioned space, and extracts the returned air
from the space through ductwork and space diffusion devices.
 A fan-powered variable-air-volume (VAV) box, often abbreviated as fan-
powered box, employs a small fan with or without a heating coil.
 Draws the return air from the ceiling plenum, mixes it with the conditioned
air from the air-handling unit, and supplies the mixture to the conditioned
space.
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54.  Constant volume (CV)
 pump a constant flow of air into each room
 Temperature changes are effected by heating or cooling the air
 Frequently mix a percentage of outside air with recycled indoor air.
 Variable volume (VAV)
 Maintain thermal comfort by varying the amount of heated or
cooled air supplied to each space.
 Function primarily based on this mixing principle, they can also be
combined with systems that change the temperature of the air
they introduce into the room.
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55.  Space diffusion devices;
 slot diffusers mounted in the suspended ceiling
 purpose is to distribute the conditioned air evenly over
the entire space according to requirements
 The return air enters the ceiling plenum through many
scattered return slots.
 Exhaust systems have exhaust fan(s) and
ductwork to exhaust air from the lavatories,
mechanical rooms, and electrical rooms.
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56.  Water system includes:
 chilled and hot water systems
 chilled and hot water pumps
 condenser water system and
 condenser water pumps.
 Purpose of the water system is:
 to transport chilled water and hot water from the central plant
to the air-handling units, fan-coil units, and fan powered boxes
and
 to transport the condenser water from the cooling tower, well
water, or other sources to the condenser inside the central
plant.
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57.  The refrigeration system in a central plant is
usually in the form of a chiller package.
 Chiller packages cool the chilled water and act as
a cold source in the central hydronic system.
 The boiler plant, consisting of boilers and
accessories, is the heat source of the heating
system.
 Either hot water is heated or steam is generated
in the boilers.
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58.  Modern air conditioning control systems for the air and water
systems and for the central plant consist of:
 electronic sensors,
 microprocessor-operated and
 microprocessor-controlled modules
 Can analyse and perform calculations from both digital and
analog input signals, i.e., in the form of a continuous variable.
 Control systems using digital signals compatible with the
microprocessor are called direct digital control (DDC) systems.
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59.  DDC controllers regulate the air-handling units and the
terminals.
 Communicate with the central operating station through
interface modules.
 In case of emergency, the fire protection system
detects alarm conditions.
 The central operating station gives:
 emergency directions to the occupants
 operates the HVAC&R system in a smoke control mode and
 actuates the sprinkler water system.
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60. SOME COMPARISON
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61. 1. Comfort air conditioning systems and
2. Process air conditioning systems.
Comfort Air-Conditioning – a process of
controlling the air temperature, relative
humidity, ventilation, air movement and air
cleanliness of a given space in order to provide
the occupants with a comfortable indoor
temperature.
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62. Air Conditioning
Human Comfort Industry
Laboratories
Printing
Manufacturing
Textile
Clean room
Government building Photography
Hospital Computer Laboratories
Hotel Power plant control room
Domestic Usage Food industry
Automotive
Chemistry & Process
Sport- Ice sky
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63.  Heat gains from sunlight, electric lighting and
business machines, may cause unpleasantly high
temperatures in rooms, unless windows are opened.
 If windows are opened, then even moderate wind
speeds cause excessive draughts, becoming worse
on the upper floors of tall buildings.
 If windows are opened, noise and dirt enter and are
objectionable, becoming worse on the lower floors
of buildings, particularly in urban districts and
industrial areas. 63

64.  The relief provided by natural airflow through open
windows is only effective for a depth of about 6
metres inward from the glazing.
 The inner areas of deep buildings will not really
benefit at all from opened windows.
 Coupled with the need for high intensity continuous
electric lighting in these core areas, the lack of
adequate ventilation means a good deal of
discomfort for the occupants.
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65.  Mechanical ventilation without refrigeration is only a
partial solution.
 Must provides a controlled and uniform means of air
distribution, in place of the unsatisfactory results
obtained with opened windows
 Internal air/room temperatures must also suitable.
 Normally room temperature will be several degrees
lower than that outside
 Hence natural or mechanical ventilation is needed as
well as to insulate the building from heat gain. 65

66.  Sick building syndrome is very common in
poorly designed air conditioned buildings due
to inadequate ventilation and use of improper
materials.
 The sick building syndrome is characterised
by the feeling of nausea, headache, eye and
throat irritation and the general feeling of
being uncomfortable with the indoor
environment.
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