How to Choose the Right Compressed Air Filter – Complete Guide

Choosing the right compressed air filter is essential for maintaining clean and reliable compressed air, protecting your equipment and reducing unnecessary operating costs. But how do you choose the right filter, and what should you consider when selecting a complete filtration solution for your compressor and compressed air system?

Are you unsure which compressed air filter is right for your system? Get help choosing and sizing the right solution.

In this guide, we cover the most important factors to consider when choosing a compressed air filter, including filtration grade, air flow, pressure, temperature, oil, water, particles and the requirements of ISO 8573-1.

What Is a Compressed Air Filter?

A compressed air filter is used to remove different types of contaminants from compressed air. Depending on the filter type, it can remove:

  • Solid particles and dust
  • Oil aerosols
  • Liquid oil
  • Water droplets and condensate
  • Oil vapour
  • Other impurities

Compressed air naturally contains contaminants from both the surrounding environment and the compression process itself. Proper compressed air treatment is therefore important for protecting machines, valves, pneumatic components and products that come into contact with the compressed air.

However, it is important to understand that one filter cannot necessarily remove all types of contamination. For example, controlling water vapour normally requires a suitable compressed air dryer, while removing oil vapour may require an activated carbon filter.

Why Is It Important to Choose the Right Compressed Air Filter?

An incorrectly selected or undersized compressed air filter can negatively affect air quality, energy consumption and the overall reliability of your compressed air system.

A correctly sized compressed air filter can help to:

  • Protect pneumatic components
  • Reduce the risk of unplanned downtime
  • Extend the service life of machines and components
  • Maintain the required compressed air quality
  • Protect end products from contamination
  • Reduce pressure drop in the compressed air system
  • Lower unnecessary energy costs

Modern compressed air filtration is therefore not simply about removing as many contaminants as possible. The filter’s differential pressure, flow capacity and total cost of ownership are also important considerations.

1. Start by Determining the Required Air Quality

Before choosing a filter, you first need to determine the level of air quality your application requires.

How Clean Does the Compressed Air Need to Be?

The required air quality depends on how the compressed air will be used.

For example, compressed air used for general workshop tools does not necessarily have the same requirements as compressed air used in food production, painting or pharmaceutical manufacturing.

ISO 8573-1 is the international standard used to classify compressed air purity. The standard defines requirements for:

  1. Particles
  2. Water
  3. Oil

An ISO specification can, for example, be written as ISO 8573-1 [1:2:1], where the three numbers indicate the requirements for particles, water and oil respectively.

Example

If your compressed air system needs to meet:

ISO 8573-1 [1:2:1]

this means that the system must meet:

  • Class 1 for particles
  • Class 2 for water
  • Class 1 for oil

The lower the class number, the stricter the requirements for the respective contaminant.

2. Which Contaminants Should the Compressed Air Filter Remove?

When selecting a compressed air filter, you need to identify the type of contamination you want to remove.

Particles

Particles can come from the surrounding environment, the compressor, the piping system or corrosion within the installation.

A particle filter can be used to reduce the amount of solid particles in the compressed air.

Oil Aerosols

If the compressor is oil-injected, the compressed air may contain oil aerosols.

A coalescing filter can be used to separate oil aerosols and other fine liquid particles from the compressed air.

Oil Vapour

Oil vapour is different from oil aerosols. If very low oil concentrations are required, an activated carbon filter may be necessary as part of the compressed air treatment system.

Water and Condensate

A standard compressed air filter should not be considered a complete solution for problems involving water vapour.

If you require a specific pressure dew point, you will normally need a suitable compressed air dryer in combination with filtration.

3. Choose the Right Filter Type

There are several types of compressed air filters, and each type is designed to perform a specific function.

You can see our range of complete compressed air filters if you are looking for a complete filtration solution for your compressed air system.

Pre-filter

A pre-filter is typically used to remove larger particles and liquid droplets before the air passes through finer filtration stages.

Coalescing Filter

A coalescing filter is primarily used for fine filtration of particles and oil aerosols.

It can be particularly relevant in applications where higher compressed air purity is required.

Fine Particle Filter

A fine particle filter is used when further reduction of small particles is required.

Activated Carbon Filter

Activated carbon is used, among other things, to reduce oil vapour when very low oil concentrations are required.

Sterile Filter

In specific applications, sterile filtration may be required, for example in processes with very high hygiene and product protection requirements.

It is therefore rarely optimal simply to choose the filter with the lowest micron rating. The filter type should match the specific contaminants and the required compressed air quality.

4. Calculate the Required Air Flow

One of the most common mistakes when selecting a compressed air filter is overlooking the required air flow.

The filter must be able to handle the required flow capacity, typically specified in:

  • m³/h
  • l/min
  • m³/min

The filter capacity must be suitable for the actual air flow in the system.

If the filter is too small, it can create unnecessarily high pressure drop, which may increase energy consumption.

Flow capacity, pressure level, temperature and filtration grade are all important factors when sizing compressed air filters.

A Good Tip

Do not size the filter solely according to the compressor’s nominal capacity.

Are you unsure about the correct filter size or flow capacity? Contact us and we will help you find a solution that is suitable for your system.

Also consider:

  • Actual air consumption
  • Peak loads
  • Number of air consumers
  • Future system expansions
  • Pressure before and after the filter

5. Pay Attention to Pressure Drop

A compressed air filter should provide effective filtration while maintaining the lowest practical pressure drop.

As a filter becomes loaded with particles and oil, the differential pressure across the filter element can increase.

A high pressure drop means that the compressor has to work harder to deliver the required system pressure.

When selecting a compressed air filter, you should therefore consider:

  • Initial pressure drop
  • Maximum flow rate
  • Filter element service life
  • Differential pressure at different flow rates
  • Options for monitoring filter condition

Low pressure drop is an important factor in the overall operating cost of a compressed air filtration system.

6. Check the Operating Pressure

A compressed air filter must be rated for the pressure at which your system operates.

Always check that:

Maximum permitted operating pressure ≥ system operating pressure

If, for example, you have a high-pressure compressed air system, you must choose a filter specifically designed for the required pressure level.

The filter’s pressure rating should always be verified in the manufacturer’s technical specifications.

7. Consider the Operating Temperature

Temperature also plays an important role when selecting a compressed air filter.

Compressed air systems can experience significant temperature variations depending on:

  • Compressor type
  • Installation location
  • Aftercooler
  • Ambient temperature
  • Installation conditions

Always check the filter’s permitted operating temperature and make sure it is suitable for your installation.

8. Do You Need One or More Filters?

Many compressed air systems require several stages of filtration to achieve the desired air quality.

A typical compressed air treatment system may, for example, consist of:

Compressor → aftercooler/separator → pre-filter → coalescing filter → dryer → fine filter → point of use

The exact configuration depends on the required air quality and the specific application.

If the compressed air needs to meet strict quality requirements, a combination of filters and a compressed air dryer may be necessary.

9. Choose a Filter Based on Your Application

The right compressed air filter depends largely on what the compressed air will be used for.

Application Typical areas of focus
Workshop and pneumatics Particles, water and oil
CNC machines Clean and dry compressed air
Painting Oil, water and particles
Food production Very high air quality and product protection
Pharmaceutical manufacturing Very strict purity requirements
Instrument air Dry and clean compressed air
Process air Depends on the process
Electronics manufacturing Very clean and dry air

Different contamination categories may have different requirements within the same installation. Therefore, you should not select a filter based on a single specification alone.

10. Do Not Choose a Finer Filter Than Necessary

It can be tempting to choose the finest filter available.

However, more filtration is not necessarily better.

A finer filter can result in:

  • Higher purchase cost
  • Greater pressure drop
  • Higher operating costs
  • More frequent filter element replacement

The goal should therefore be:

The required compressed air quality at the lowest possible total cost of ownership.

Start by determining the required ISO 8573-1 air quality class and then select the appropriate filter and dryer solution based on that requirement.

11. Remember Filter Maintenance

Even the best compressed air filter will not perform optimally if the filter element is not properly maintained.

A clogged filter can cause increasing pressure drop and consequently higher energy consumption.

You should therefore have a maintenance plan covering differential pressure monitoring and regular replacement of filter elements.

  • Checking drains
  • Inspecting the filter housing
  • Checking seals

Filter manufacturers offer various solutions for monitoring filter condition, making it easier to determine when the filter element should be replaced.

How to Choose the Right Compressed Air Filter – Quick Checklist

Before purchasing a compressed air filter, you should know:

  • What application will the compressed air be used for?
  • What ISO 8573-1 air quality is required?
  • Which contaminants need to be removed?
  • What is the required air flow?
  • What is the system’s operating pressure?
  • What temperature does the system operate at?
  • How much pressure drop is acceptable?
  • Are several filtration stages required?
  • Is a compressed air dryer required?
  • How often does the filter element need to be maintained or replaced?

Which Compressed Air Filter Should I Choose?

There is no single universal compressed air filter that is suitable for every compressor and application.

The best choice depends on the combination of air quality, flow, pressure, temperature, contamination and total operating cost.

As a starting point, follow this selection process:

  1. Determine the application → 2. Establish the ISO requirement → 3. Identify the contaminants → 4. Calculate the required flow → 5. Check pressure and temperature → 6. Select the filter type → 7. Check pressure drop and total operating costs.

This approach helps you select a compressed air filter that not only provides effective filtration but also fits the requirements of the rest of your compressed air system.

See our range of complete compressed air filters and find a solution that suits your system.

Conclusion

Choosing the right compressed air filter involves more than simply looking at the filter’s micron rating. You first need to determine the air quality your application requires and then size the filter according to air flow, pressure, temperature and the type of contamination that needs to be removed.

ISO 8573-1 is a useful starting point because it provides a systematic way of describing requirements for particles, water and oil.

In short: Do not choose the largest or finest filter – choose the filter that is correctly sized for your specific application.

Are you still unsure which compressed air filter to choose? We can help you find the right solution based on air quality, flow, pressure and application.