Atlas Copco compressed air filter installed in South Yorkshire

A Guide To… Compressed Air Filters


Compressed air filters, the subject of this blog, are essential pieces of kit for any company running a compressor.

Air filters not only remove excess moisture in the compressed air, but also harmful substances including:Atlas Copco compressed air filters

  • oil
  • dust
  • rust
  • vapour

These can all cause wear and damage to equipment connected to your compressed air system such as:

  • control valves
  • air cylinders
  • air tools

Air filters are usually located in the pipework (inline compressed air filters). The filter elements need to be renewed on a regular basis as part of your maintenance schedule. Poor filtration of air will cost you money in the long run.

Compressed air filters – or line filters as they are also known – are available in a range of sizes and can also vary in quality, which is why it’s a good idea to get advice from the compressed air experts at Simm Engineering before making a purchase.

In applications where the compressed air needs to be clean and dry, filters can be used in tandem with a compressed air dryer.

Different types of filters include:

  • particulate filters
  • coalescing filters
  • activated carbon filters

To take these in turn:

Particulate filters or pre-filters
– these can remove particles such as dust from compressed air down to 1.0 µm. Water and oil, particles are removed down to 0.1 µm.

Coalescing filters or after filters – these clean compressed air of water and oil aerosols to 0.01 µm.

Atlas Copco compressed air filtersActivated carbon filters – mainly used where breathing air is required or in food manufacturing units, these remove oil vapour and hydrocarbon odour from compressed air by filtering it through a composite carbon material.

Each compressed air filter works in several stages:

  1. A mesh filter creates a coalescence effect, absorbing larger particles and causing the water to condense into droplets that can be channelled into a separation chamber.
  2. As the compressed air slows in speed, the particles condense on a pad resembling a honeycomb. The droplets of water then descend through the drainage system and are discharged via an automatic or electric drain valve.
  3. The air is then accelerated as it passes through fibre and emerges ready for use.

For more information on the different types of compressed air filters, please contact Simm Engineering and we will be happy to give advice on the phone or in a site visit. You can also find out more about the Atlas Copco range of compressed air filters here.