Today, people spend 90% of their time indoors. Measurements made in Indoortron, the Indoor Air Quality Laboratory established by the European Union in Ispra, Italy, have shown that people are exposed to air pollution 2 to 5 times more indoors than they are outside.

For this reason, studies on air pollution are no longer limited to only outdoor air pollution, but also focus on indoor air pollution. There are some symptoms of discomfort in people who are exposed to air pollution. They are mainly divided into two.

1.3.1 Sick Building Syndrome (RLS)
 RLS symptoms cannot be fully diagnosed,
 The cause of RLS cannot be fully defined,
 RLS occurs as acute (short-term) symptoms and usually disappears when you leave the building.

Symptoms that occur as discomfort:
- Headache
- eye burn
- wheezing
- Skin allergy
- Upper respiratory tract problems
- nausea
- exhaustion
- blurred vision
- Others

 The causes of these disorders are not easily identified.
 Healing occurs after a while after leaving the building.

1.3.2 Building Associated Diseases (BBD)
 CKD is due to an identifiable cause,
 CKD can be diagnosed clinically,
 BKD occurs as chronic (long-term) symptoms and causes severe diseases,
 CKD treatment is long-term.

Some of the symptoms of Building Associated Diseases are as follows:
- Legionnaires' disease
- allergic pneumonia
- allergic rhinitis
- Fire
- Asthma
- Mycotoxin poisonings
- Endotoxin poisoning

 Requires immediate intervention
 Characterized by clinical manifestations
 It is much more serious than Sick Building Syndrome: it has a long treatment period

1.3.3 Major Factors Causing Sick Building Syndrome

 Insufficient ventilation
 Chemical pollutants originating from inside
 Chemical pollutants originating from outside
 Biological pollutants
 Particles, powders, glass wool, asbestos, etc. fibrous substances
 Radon gas

1.3.4 Precautions to be Taken Against Sick Building Syndrome

 Ventilation design in accordance with ASHRAE-Standard 62 (fresh air per person)
 Proper selection and placement of blowing and suction vents (fire speed, direction, bypassing)
 Proper placement of outdoor louvers (away from pollutant sources)
 Design of exterior air louvers for low air velocity (maximum 2.5 m/s)
 Designing cooling coils and humidifiers for low air velocity (maximum 2.5 m/s)
 Not using fibrous acoustic insulation in ducts
 Kitchen, toilet, smoking room, copy room, chemical warehouse, etc. direct exhaust of spaces
 Ensuring the minimum flow rate to provide sufficient mixing in ceiling diffusers (minimum 5 L/s per m2)
 Lack of stagnant air in the sitting area
 Use of dust filters with at least 60% efficiency
 Use of 100% outdoor air when the outside weather conditions are suitable (free cooling)
 Sweeping in offices without heating or cooling with 100% outside air at night
 Using natural ventilation methods as much as possible (opening windows, using the chimney effect)
 To use displacement type ventilation methods