Measure oxygen O₂ icon

Oxygen (O₂)

Molecular oxygen (O₂) is a colourless and odourless gas that is present in 21 % of the air. On the Earth's surface, oxygen is the most abundant element by mass.

Can be measured with:

✓ measurable with air-Q pro as well as air-Q science


Almost all animal life forms need oxygen to live. It is absorbed through respiration or, if it is dissolved in water, through resorption. In high concentrations, however, oxygen is toxic to most living organisms.

All combustion and corrosion processes take place with the participation of O₂.

In addition to its medical use, it is particularly important for the metalworking industry, as oxygen can form compounds with almost all elements. In addition, oxygen is involved in many combustion and corrosion processes.

Limit values for oxygen:

There are no legal limits in Germany. Possible damage caused by oxygen depends mainly on the pressure. DGUV Rule 113-004 for occupational safety specifies a value of 17 % oxygen.

The exhaled air of a person still has about 16 % oxygen. The oxygen concentration of the air breathed in before that is around 21 % on average.

Even an oxygen concentration of 100 %, as is necessary, for example, when ventilating patients, can lead to damage to the brain in the medium term.

Designationning Oxygen limits
DGUV Rule 113-004 for work in silos and confined spaces 17 %

Consequences of too high or too low O₂ concentrations:

An undersupply has effects on the organism. If the oxygen content of the air drops below 17%, the first signs of fatigue appear. In addition, the error rate in visual tasks and logical thinking increases. A prolonged reaction time can be expected.

A significantly reduced oxygen content in the breathing air further leads to symptoms of acute altitude sickness. These include headache, fatigue and loss of appetite as well as nausea and dizziness. In severe cases, cerebral and pulmonary oedema may develop. At oxygen concentrations of less than 13 %, severe, non-reversible damage can occur, which can lead to death - asphyxiation occurs.

The danger of oxygen poisoning only exists if O₂ is present at a partial pressure that significantly exceeds the normal air pressure. This is of particular importance for divers. Symptoms include rapid and shallow breathing as well as phenomena such as eye flickering, muscle twitching and auditory hallucinations. Furthermore, nausea and dizziness up to unconsciousness and epilepsy-like seizures can occur.

In chronic lung diseases with increased CO₂ partial pressure, such as COPD, ventilation with oxygen can have serious consequences for patients. The sudden increase in the supply of O₂ can lead to respiratory arrest under certain circumstances.

Emergence of O₂:

The earth's crust alone consists of 48.9 % oxygen. In the Earth's shell, the proportion is around 30 %. On Earth as a whole, only iron has an even greater occurrence. However, this oxygen is chemically bound and not a breathable gas. During the Earth's primeval period, cyanobacteria released oxygen into the atmosphere as a waste product of their photosynthesis over a period of more than a billion years, thus producing the free oxygen that is the basis for much life today.

Plants release oxygen during photosynthesis. This is a biochemical reaction caused by sunlight, in which the plant replenishes its own energy stores from CO₂ and water, releasing the oxygen it does not need.

Sensor used:

Oxygen is measured by means of a sensor based on optical fluorescence. The advantage of this principle is the long lifetime compared to an electrochemical sensor and lower costs. There are no disadvantages. The sensor we use has no known cross-sensitivities to other gases.

Measure oxygen:

With the air-Q measuring device you can measure oxygen, but also all other relevant components of the room air such as carbon monoxide. As a particularly powerful and comprehensive device, the air-Q air analyser has sensor technology that can measure the O₂ content of the room air.

A lot of information about the technology can be found here. You can order the air-Q in the online shop.

air-Qs, which use the sensor for

Oxygen (O₂)


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air-Q Air Quality Meter

Monitor air quality, all air components and environmental influences with the air-Q. For your health and performance.