Compressor air quality – what you need to know

The air around us not only contains the well-known gases of oxygen, carbon dioxide and nitrogen but also a host of other gases and particulate matter. Sources of man-made particulates come mainly from industry, diesel oil and petrol engines, friction material from brakes and tyres, and dust from road surfaces. There are also natural sources of particulate matter, such as pollen, soil and sand.  Water, whether in the form of vapour or liquid particles, is prevalent to some degree in all ambient environments. All of these are circulating in the atmosphere and can find their way into the air taken into your compressor, unless action is taken to remove these contaminants before they hit your air tools.


Why is air quality important?

When atmospheric air is physically forced into a smaller volume, the molecules take up less space and the air is compressed.  As well as the air being compressed into a smaller space, so too is any dust, water or oil particles present in the air.

The quality of compressed air, that is the ratio of pure compressed gas to foreign particulate and moisture content, must be matched to the hardware or tools which use it. A source of compressed air is only good if it doesn’t damage any downstream equipment or products such as fibre optic blowers or pneumatics. Moisture, oils and particulates can all reduce the efficiency of your compressed air system and therefore your tools. By taking the time to understand the correct specification of air required by your equipment from the outset will reduce downtime in the longer term.  It will also minimise the risk of any rust and dirt passing to any downstream air tools which would otherwise cause parts to seize or rust.


How is air quality measured?

Air quality is measured via a classification system.  The purity classes range from the cleanest, least contaminated class 0, to the most impure, class 9.  It is important to understand that class 0 air still has a level of impurity, albeit a fraction of the higher classes and at this level the acceptable purity levels must be agreed between the user and the original equipment manufacturer.  In essence however Class 0 means purer air than Class 1, but this does not mean zero contamination.


What to consider

Different applications require compressed air of differing qualities.  Whilst the air flow and pressure requirement for an application can be easily identified, ensuring you are specifying the correct air quality can be a bit harder.  Most air tools specify the correct air quality requirements in their user manual.

The key areas that it is important to consider when identifying the right air quality for your compressor are:

  • Water in the air
  • Dewpoint / pressure dewpoint
  • Oil in the air
  • Dust and other particulate matter


Benefits of ensuring high quality air

  • It minimises the maintenance required of air tools (clean, dry air)
  • It minimises breakdowns, resulting in higher machine uptime
  • Tools and hardware have longer service life


Downsides of ensuring high-quality air

  • There is an additional cost of equipment like filters and air dryers
  • Dryers or filters fitted may use a proportion of the air flow from the compressor which may limit the available air flow from your compressor
  • Replacement filter costs – filters will need to be regularly replaced to ensure that the air quality levels don’t drop


Vert has a team of engineers well versed in air quality and how to get the right specification for your Vert compressor.  Contact us at

For the latest Vert news follow our LinkedIn page