Air in pneumatics

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Air is the term used for the gas mixture in the earth's atmosphere.
The two gases nitrogen and oxygen alone make up a total of approx. 99% (approx. 78 and 21% respectively). The rest is mainly argon and traces of other gases.
In its natural state, air is colourless, odourless and tasteless.
However, air is not weightless; there are different measuring principles for determining the weight of air.

How much does air weigh?

Festo works according to DIN 1343. According to these parameters, one cubic metre of air (1000 litres) weighs 1.292 kg 

Air pressure

Several kilometres of air surround the earth. The air pressure is generated through the weight force of this blanket of air, which presses onto the earth's surface.
At the earth's surface, the air pressure is approx. 1 bar. The actual air pressure constantly fluctuates slightly, and is dependent on the weather, temperature, air humidity and also on the altitude of the measured location.
In pneumatics, the pressure of the compressed air is generally measured or displayed using pressure gauges.

Standard litres

A standard litre is the volume of a gas under defined parameters (pressure, temperature)

According to DIN 1343 According to ISO 6358
Pressure 1.01325 bar (abs) 1.0 bar (abs)
Temperature 0 °C 20 °C
Gas constant 287.07 J (kg K) 288 J (kg K)
Density 1.292 kg/m³ 1.185 kg/m³

Air humidity

0% 65 %


Air as a tool

We all know that air can generate a lot of force. In the form of wind, air has driven ships over the sea or powered mills for hundreds of years. In the form of storms, air can snap trees without any problem. In Nature, this force is mainly generated through air velocity. In industry, on the other hand, we work primarily by increasing (compressed air) or decreasing (vacuum) the air pressure.

What is in air apart from air?

After a rain shower, the mountains on the horizon can be seen more clearly than usual. This is not an optical illusion. Part of this phenomenon is simply caused by the fact that the rain has washed a lot of dirt particles out of the air. That means that few or many solid particles are always present in the air.
In addition, air also contains water - not water in the form of rain or mist, but as a proportion of invisible steam.
This proportion of water is stated as air humidity.
Both the solid particles and water are disadvantageous for industrial use. Therefore, compressed air goes through
an additional stage of preparation. This means that it is cleaned, dried, the pressure is adjusted and, if applicable, it is lubricated. Air preparation units are used for this purpose. The quality achieved is represented in quality classes.

What do the quality classes for compressed air mean?

Quality classes for compressed air according to ISO 8573-1:2010

ISO 8573


Solid particles Water Oil
Maximum number of
particles per m³




Pressure dew point





Total oil content
(liquid, aerosol and vapour)


0.1-0.5 µm  0.5-1 µm  1-5 µm
0 In accordance with specifications by the device user, stricter requirements than Class 1
1  ≤ 20,000 ≤ 400 ≤10 - ≤ -70 -  0.01
2  ≤ 400,000 ≤ 6,000 ≤ 100 - ≤ -40 - 0.1
3 - ≤90,000 ≤1,000 - ≤ -20 - 1
4 - - ≤ 10,000 - ≤ +3 5
5 - -  ≤100,000 - ≤ +7 - -
6 - - - ≤ 5 ≤ +10 - -
7 - - - 5 - 10 - ≤ 0.5 -
8 - - - - - 0.5 - 5 -
9 - - - -- -  5 - 10 -
X - - - > 10 -  > 10 > 10


If the ambient air is simply compressed, the gas mixture consists of approx. 78% nitrogen and 21% oxygen. If these gases are available in a pre-prepared form, this raises the question:
can Festo products be operated with nitrogen?
Provided the following parameters are adhered to,
using nitrogen as the pressure medium means that our products can be operated without any significant restriction to their service life.
The nitrogen used must be available in a gaseous state
The operating pressure and operating temperatures must comply with the values specified for compressed air
on the data sheet
Contamination of the nitrogen used in terms of residual humidity,
residual oil content etc. complies with the specifications in the catalogue for operation
with compressed air


When using components with oxygen, a couple of rules must be followed. One of these rules is that our standard components are not suitable for use with oxygen. You can obtain information as to which components are suitable from the Technical Hotline 0711 347-3000


How much does compressed air cost?

On average, it costs approx. 2.5 cent per 1 m³.

Did you know?

What pressure does a human lung generate?
The lung is a natural compressor able to process 100 l/min. This generates a
pressure of 0.02 - 0.08 bar.
Which is lighter - humid or dry air?
Air gets lighter as it gets warmer. However, air also gets lighter as
it becomes more humid. That is why we talk about water parts that are not visible
(in gaseous form), not to be confused with mist (small drops of
liquid water). Air essentially consists of a mixture of
nitrogen and oxygen and has a molecular weight of approximately 29 grams,
whereas the molecular weight of water vapour is only around 18 grams.