What Do Grade and Micron Mean on a Compressed Air Filter?

When choosing a compressed air filter, you will often come across terms such as filter grade, micron rating and different filtration classes. But what do these terms actually mean, and how do they affect the quality of your compressed air?

In simple terms, the micron rating of a compressed air filter indicates the size of particles the filter is designed to remove, while the filter grade indicates the type and level of filtration. The cleaner your compressed air needs to be, the more important it is to choose the correct combination of filters.

What Does Micron Mean on a Compressed Air Filter?

Micron (µm) is a unit of measurement used to describe particle size. One micron equals 0.001 mm.

For example, when a compressed air filter is described as a 5 micron filter, it generally means that the filter is designed to retain particles around this size and larger. However, the actual filtration performance depends on the filter design, filter media and test standard used.

It is important to understand that a specification such as “5 micron” does not necessarily mean that 100% of all particles measuring 5 µm will be removed. The actual efficiency of a compressed air filter depends on several factors, including the filter media, construction, air flow, operating pressure and operating conditions.

Examples of Particles and Contaminants in Compressed Air

Compressed air can contain many different types of contamination, including:

• Dust and dirt
• Rust particles from the compressed air piping system
• Oil particles and oil aerosols
• Water droplets
• Condensation
• Microorganisms and other very small particles

A compressed air filter with a lower micron rating can generally remove finer particles than a filter with a higher micron rating. However, this does not mean that the filter with the lowest micron rating is always the best choice.

What Does Filter Grade Mean on a Compressed Air Filter?

Filter grade describes the filtration stage and the type of contamination that the filter is designed to handle.

Different manufacturers use different names and classifications for their filter grades. For this reason, you should always check the manufacturer’s specifications rather than comparing filter grades based solely on a letter or grade name.

A compressed air filtration system can consist of several filtration stages, with each filter performing a specific function:

Pre-filter → fine filter → oil/aerosol filter → activated carbon filter

Using several filtration stages allows contaminants to be removed progressively, reducing the load on the finer filters and helping to maintain efficient filtration throughout the system.

What Is the Difference Between Micron and Filter Grade?

Micron and filter grade are closely related, but they describe different aspects of a compressed air filter.

Term	What does it describe?
Micron (µm)	The size of particles the filter is designed to remove
Filter Grade	The filter’s filtration stage, type and typical application
Filter Efficiency	How effectively the filter removes a particular type of contamination
Pressure Drop	The reduction in air pressure as compressed air passes through the filter

When searching for a compressed air filter by micron rating, it is therefore not enough to look at the micron value alone. You should also consider the filter’s efficiency, flow capacity, pressure drop and the type of contamination it is designed to remove.

Which Micron Rating Should I Choose for Compressed Air?

The correct micron rating depends on the application and the required compressed air quality.

For general industrial applications, a coarser filter may be sufficient to remove larger particles and protect pneumatic equipment. If the compressed air is used for applications such as spray painting, instrument air or other processes with high cleanliness requirements, additional filtration stages may be required.

It is therefore better to select a compressed air filter based on the required air quality and application rather than simply choosing the filter with the lowest micron rating.

A Typical Compressed Air Filter System

A compressed air system may, for example, include the following filtration stages:

1. Pre-filter – removes larger particles and protects the filters further downstream.
2. Fine filter – removes smaller particles and oil and water aerosols.
3. Activated carbon filter – used when oil vapours and odours need to be reduced to a very low level.
4. Sterile filter – used in specialised applications where very high levels of compressed air purity are required.

The specific compressed air filter configuration should always be selected according to the required air quality, application and operating conditions.

Is a 1 Micron Filter Better Than a 5 Micron Filter?

Not necessarily.

A 1 micron compressed air filter is designed for finer filtration than a 5 micron filter. However, a finer filter can also create a higher pressure drop and may require more frequent maintenance if it is used as the first filtration stage.

The best compressed air filter is therefore not necessarily the one with the lowest micron rating. The best filter is the one that matches your compressed air quality requirements while providing sufficient flow capacity for your system.

Why Is Filter Grade Important for Compressed Air?

Choosing the correct filter grade for compressed air is important because contaminants in compressed air can affect pneumatic tools, machinery, components and the production process itself.

A correctly designed and sized compressed air filtration system can help to:

• Protect compressed air tools and pneumatic components
• Reduce the risk of equipment problems and operational disruptions
• Protect products and production processes
• Reduce oil, water and particles in compressed air
• Achieve the required compressed air quality
• Extend the service life of downstream components

Remember Air Flow and Pressure Drop

When selecting a compressed air filter, micron rating and filter grade are not the only specifications you should consider.

Air flow capacity is equally important.

The filter must be able to handle the volume of compressed air supplied by the compressor and used by your compressed air system. If the filter is undersized, the pressure drop can become unnecessarily high.

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

• Required air flow
• Operating pressure
• Connection size
• Micron rating
• Filter grade
• Filter efficiency
• Expected pressure drop
• Type and concentration of contamination
• Required compressed air quality

How to Choose the Right Compressed Air Filter

If you are unsure which compressed air filter is right for your system, start by answering these questions:

1. What will the compressed air be used for?

Is it used for general pneumatic tools, production equipment, spray painting, instrument air or another specialised application?

2. How clean does the compressed air need to be?

The higher the compressed air quality requirements, the more advanced the filtration system may need to be.

3. Which contaminants need to be removed?

Is the main concern dust and particles, water, oil aerosols, oil vapours or odours?

4. What is the required air flow?

The compressed air filter must be correctly sized according to the actual air consumption and required flow rate.

5. Which filter grade is required?

Always check the manufacturer’s specifications and the relevant compressed air quality requirements for your application.

Once you have established the requirements for micron rating, filter grade, air flow and compressed air quality, you can choose between original filter elements and alternative filter elements, depending on your requirements regarding price, compatibility and manufacturer.

Micron Is Only One Part of a Compressed Air Filter Specification

When comparing compressed air filters, it can be tempting to focus only on the micron rating. However, the performance and suitability of a compressed air filter cannot be determined by micron alone.

A filter with the correct micron rating but insufficient flow capacity or the wrong filter type may not be the right solution for your compressed air system.

In short:

Micron indicates the particle size a filter is designed to remove, while filter grade describes the filter’s filtration stage and intended application. Choosing the right compressed air filter depends on the required air quality, filter efficiency, air flow, pressure drop and the overall design of the compressed air system.

Do You Need Help Choosing a Compressed Air Filter?

Are you unsure which micron rating or filter grade for compressed air you should choose? The right solution depends on your specific compressed air system, application and required air quality.

Explore our selection of compressed air filters and filter elements, or contact us if you need help finding the right filtration solution for your compressed air system.