Myths of compressed air technology

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Air Treatment Myths:


Filter elements should only be changed when differential pressure is high.


You install compressed air filtration to improve air quality. DP gauges / indicators are blockage indicators not air quality indicators. To ensure your compressed air quality, filter elements should be changed annually in line with manufacturer's instructions.



Coalescing filters are ONLY for oil removal.


Coalescing filters have a even higher rate of capture with solid contaminants than with liquids.



Oil contamination is not present in atmospheric air.


Atmospheric air typically contains between 0.05mg / m3 and 0.5mg / m3 of oil vapor from sources such as exhausts and industrial processes. As oil free compressors are used in the compressed air systems, the use of oil free compressors does not guarantee oil free air.



Liquid oil and oil aerosol are the only contaminants present in a compressed air system.


Generally, there are parts of a compressed air system that need to be removed or reduced for the system to run efficiently.

The ten contaminants are:

Water vapor

Liquid Oil

Oil vapor

Rust Atmospheric Dirt

Water aerosols


Oil aerosols

Liquid Water


Only two of these contaminants, liquid and oil aerosol are introduced by a lubricating compressor. The purification equipment required to reduce or remove the remaining contaminants by virtue of their operation. Therefore, regardless of the type of compressor installed, the purification equipment is required.



Compressed air contamination is a compressor issue.


In a typical compressed air system, compressed vacuum comes from four different sources, these being:

Source 1 - Atmospheric Air

Air compressors draw in huge amounts of atmospheric air, which continuously fills the system with contaminants such as water vapor, micro-organisms, atmospheric dirt & oil vapor.

Source 2 - The Air Compressor

In addition to the contaminants drawn in through the compressor intake, the compressor also adds additional wear particulates from its operation. Additionally, oil lubricated compressors carry liquid oil, oil aerosol and oil vapor from the compression process. So after the compression stage, the after-cooler wants to condense water vapor, introducing it into the compressed air in both a liquid and aerosol form.

Source 3 - Compressed air storage devices

Source 4 - Compressed air distribution piping

The air receiver (storage device) and the piping that distributes the compressed air around the facility both store large amounts of contamination. Additionally, they are cool and hot, which causes condensation, pipescale and microbiological growth.



Static Oil Water Separators are not suitable for synthetic lubricants / PAG's. This is evident with cloudy outlet water.


Oil water separators are designed to reduce oil to water levels to acceptable limits. Some lubricants such as synthetics / PAG's contain detergents and additives to extend the life of the compressor. Oil water separators are not designed to remove detergents and additives. Oil in water content should not be used. Lab analysis on cloudy outlet water is the only way to assess oil in water content and it is within acceptable limits.



Any dryer (refrigerated or desiccant) can be installed outdoors.


All standard dryers are designed for internal installation. However, many are often installed outside (with a lean-to-roof in some cases and without a lean-to-roof in some cases). It is lean-to-roof with freeze / snow protection, blowing rain protection, and a roof. Outside installation of standard dryers with no roof is not recommended.

UV protection in paint, fastners and electronics, and Nema 4 components throughout. A Nema 4 is not sufficient for outdoor without roof installation.



Most dryers do not provide dryness levels quoted in sales literature.


Dryer installations are often plagued with a variety of oranges which impact the level of compressed air dryness. Classic installation mistakes are: insufficient space above or in front of condenser air discharge which causes recirculation and high pressure faults