Mankind has faced indoor air problems since the day it discovered fire. It was learned in a short time that the smoke inhaled in the caves reduces human life. Mankind, who learned to remove the smoke from a hole in the ceiling of the cave, had to deal with indoor air problems in the next millennia. It was observed that among the workers working in the construction of the Egyptian pyramids, those working inside were more likely to get respiratory diseases than those working outside. The Romans invented floor heating in order to be able to heat without smoke. In the 11th century, in his book Mukaddime, Ibn-i Haldun pointed out that air pollution would cause diseases.

In the 16th century, King Charles I of England introduced a set of rules to reduce the effect of polluted air in buildings. These include ceilings higher than 3 meters, windows that are longer than they are wide, determining the window area according to the room floor area, etc. Construction rules such as these always aimed to evacuate the smoke and polluted air inside.

In the 18th century, with the discovery of carbon dioxide by Lavosier, the effects of this gas on air pollution began to be discussed and researched. Carbon dioxide was previously considered a toxic gas.

During the Crimean War in 1853, while the hospitals in Istanbul were overflowing with the wounded, it was observed that the wounded took a long time to heal in airless places. Doctors, who initially thought this might be due to the intense carbon dioxide in the air, later realized that the root cause was that the germs from the wounded had found a suitable medium for propagation due to poor ventilation.

Carbon dioxide is an odorless, colorless and non-toxic gas. Many people think that carbon dioxide is a poisonous gas, but it is a gas that our body produces. It is not carbon dioxide that is toxic, but carbon monoxide, a product of incomplete combustion. There is 38,000 ppm of carbon dioxide in our breath. The source of carbon dioxide indoors is only breathing or open fire. It has no other source. Humans produce about 0.005 liters of carbon dioxide per second on average. Therefore, carbon dioxide can be used as a factor for determining the number of people inside. Today, border police catch illegal immigrants in closed containers with carbon dioxide detectors.

Numerous experiments have been carried out since the 19th century in order to determine the amount of carbon dioxide in the inhaled air and the amount of fresh air required accordingly. In 1836, Tredgold, in his experiments on miners, determined the amount of fresh air that human metabolically needs as 2.5 L/s per person. In 1862, Pettenkofer suggested that carbon dioxide was not actually an air pollutant, but could be used as a measure of pollution. Numerous subsequent experiments have confirmed this assertion. In the closed room experiments carried out at the beginning of the 20th century, it was proved that people can tolerate carbon dioxide rates such as 10,000 ppm, and that even very high rates such as 23,000 ppm do not pose a life-threatening risk.

In the Ventilation Standard No. 62 published by ASHRAE (American Society of Heating Refrigerating and Air Conditioning Engineers) in 1989, the carbon dioxide limit for office workers is determined as 1000 ppm. OSHA (Occupational Safety and Health Agency), which determines workplace working conditions in the USA, has determined this limit as 5000 ppm, provided that it does not exceed 40 hours per week. ASHRAE Standard 62 also recognized that carbon dioxide is not a pollutant per se, but is a measure of polluted air from humans.

The standard measurement of carbon dioxide in the atmosphere is made on an island in the middle of the Pacific Ocean. While this rate was around 280 ppm before the industrial revolution, today it is increasing with the consumption of fossil fuels. Global warming caused by the greenhouse effect caused by this is a topic on everyone's agenda today. The carbon dioxide rate in the atmosphere today is around 390 ppm and unfortunately it is increasing by 2 ppm every year.

It is useful to know the carbon dioxide limits determined by ASHRAE and OSHA well, because today, the amount of outside air is adjusted in air handling units depending on the carbon dioxide rate, which is started to be measured as an indicator of air pollution in some buildings. Accordingly, as long as the carbon dioxide rate is below 1000 ppmin, there is no need for outside air. However, in many businesses, building automation systems are adjusted to a much lower carbon dioxide rate, so fresh air is pumped in even though it is not needed at all. Today, the carbon dioxide rate in the outside air in Istanbul varies between 400 and 600 ppm. In some businesses, carbon dioxide sensors are set to 500 ppm, so air handling units are always forced to work with 100% fresh air. This means a great waste in today's world where energy is extremely expensive.

There are various factors that cause indoor air pollution. These are detected by olfactory cells in the human nose. The human nose can distinguish about 500 thousand chemicals, and this odor perception depends on two parameters:
Density (quantitative) factor (I),
The repellency (qualitative) factor (K).

The intensity of the perceived odor was formulated by Weber with these two parameters as follows:
S = K log I

As can be seen from here, the perceived odor is proportional to the logarithm of the intensity. This means that if there is 1 ppm of any odor inside, you can immediately feel it as soon as you enter the room. But if there is 100 ppm of the same fragrance inside, you do not feel it as 100 times, but as 10 times.

The amount of odor that people perceive is actually a direct measure of Indoor Air Quality (IHR). In 1935, Lambert and Yaglou investigated whether the human nose could be used as an air quality sensor. In their experiments, a certain amount of odor molecules are injected into the air at a certain flow rate passing through a channel, and 10 subjects with very strong sense of smell are asked to measure the degree of smell they feel by putting their noses into the canal. This is how the Lambert odor index was developed. This index ranges from 0 to 5 and an index of 2 is considered a normal scent.

During these experiments, the idea developed that man himself is a source of odor and that it can be used as an odor measurement standard. In fact, the cause of this odor is the acid secreted by a bacteria in the armpit. 97% of men and 67% of women have this bacteria.

Here, the standard person is a person who takes a bath twice in 3 days, changes clothes every day, and performs a normal activity (such as an office worker). The amount of odor emitted by such a standard person is called 1 olf.

“Olf” is a unit used to measure the concentration at a pollution source. Danish Prof. Dr. The term "Olf" is derived by P.Ole FANGER from the Latin word "olfactus" meaning "fragrant".

If attention is paid, a person who smokes creates as much air pollution as 25 standard people. Moreover, even when this person does not smoke, it creates as much pollution as 6 standard people. These figures are sufficient to explain why smoking is banned in many workplaces. The contribution of the smoker to the ventilation bill of the place where he works is extremely obvious.

If the smell produced by humans is perceived by the human nose, it is the element that determines the air quality in any space, that is, the amount of odor perception in the space. This perception is closely related to the ventilation of that space as well as the pollution produced in olf.

The unit developed to describe this is called the decipol. Decipol is a unit used to measure perceived air quality. Danish Prof. It was developed by P. Ole Fanger.

By definition: 1 decipol = The odor perceived by the human nose when 10 L/s of fresh air is supplied to a room in which 1 olf odor is produced. Well;
1 decipol = 1 olf / 10 L/s = 0.1 olf / L/s

In short, decipol is a measure of perceived indoor air quality. Decipol values ​​in some places are as follows:

 0.01 decipoles: Air in mountains or open seas,
 0.1 decipoles: City air,
 1.0 decipoles: Healthy building air,
 1.4 decipoles: Acceptable building air (by 80%),
 10 decipoles: sick building air.

On the other hand, it has been determined that some building materials also produce air pollution. For example, the pollution emitted by the widely used chipboard and MDF is quite high.

The air pollution rates created by various building materials are as follows:

 Chipboard, MDF: 2,4 decipoles,
 Synthetic carpets: 3,4 decipoles,
 Painted wall: 2.1 decipoles,
 Mastic, etc. material: 3.0 decipoles,
 Lacquer: 3.7 decipoles,
 Tobacco smoke: 14.4 decipoles.