Oxygen is a gas that does not smell, taste or color and is present in the air at a rate of one fifth. Combines with hydrogen to form water. Oxygen is the most common element in the earth. It exists in nature in the form of O2 molecules. Very high energy is required to break the bond in the oxygen gas molecule. Therefore, oxygen reactions occur slowly and at high temperatures. If the oxygen is cooled, it becomes a blue liquid.

Oxygen gas is normally soluble in water. Water needs to have oxygen to survive. Oxygen gas is vital for all breathing organisms. Oxygen entering the body through the respiratory tract is transported to the lungs, where oxygen merges with the hemoglobin contained in the blood. It is transported through the bloodstream to other organs of the body and to the smallest cells and burns fats and proteins in the body. The energy required for living things is obtained in this way.

When something burns, it uses oxygen and releases light and heat. This important feature makes oxygen a powerful fuel for rockets and jets. Oxygen is also used for cleaning drinking water, pool water and ponds. Meanwhile, in fish farms, oxygen is used to enrich the oxygen in the water. Other areas where oxygen is used are: to achieve high efficiency in the petrochemical process, to obtain ozone for oxidant and disinfectant, to enrich the air during fermentation in the food industry, and many other areas.

In short, oxygen is important for all habitats and its absence threatens life. Normally, the percentage of oxygen required to be present in the breathed air is 20.9. In general, percent 19,5 is considered the lower limit and percent 23,5 is considered the upper limit.

The most important factor that reduces the amount of oxygen in the air is the combustion of flammable substances. In addition, oxygen consumption is high in bacterial formations. Some chemical reactions also reduce the amount of oxygen. The presence of too many people in a confined space affects the rate of oxygen consumption. The replacement of O2 with other gases, such as helium, argon and nitrogen, is also effective in reducing the amount of oxygen. These gases are not toxic but are still dangerous to human health. For example, it can be fatal if carbon dioxide or nitrogen gases are replaced with O2.

The effects of various aspects of oxygen deficiency on human health are as follows:

• Percent 15-19 between, the ability to work is reduced, coordination is impaired, heart failure, circulatory system and lung disorders begin
• Percentage 12-15 percent, respiration increases, pulse increases, perception weakens
• Percent 10-12, respiration approaches zero, lips turn purple
• The percent 8-10 thought begins to disappear, consciousness weakens, nausea and vomiting begin
• Percent 6 to 8, death occurs in eight minutes, with a partial recovery in six minutes

For these reasons, the level of oxygen gas in the air (O2) can be dangerous to human health. Especially in work environments and risky areas, the amount of oxygen in the air must be measured. These measurements are carried out by authorized test and inspection institutions. The measurements are based on the legal regulations in force and the standards published by domestic and foreign organizations.