10 Questions You Should to Know about inline compressed air filter

Author: Liang

Sep. 01, 2025

Inline Filter Selection for Compressed Air Systems

Inline compressed air filters are vital for having clean air for your applications and pneumatic tools. However, it can be difficult when trying to decide. Understanding the contaminants in your air supply and which filter types can remove them is the first step in selecting the right inline air filter for your system.

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In this article, we'll answer the following questions:

  1. How Does Compressed Air Become Contaminated?
  2. What are Inline Air Filters Used to Remove?
  3. How do Inline Air Filters Work?
  4. What is Considered Optimal Air Quality?
  5. Choosing the Right Inline Compressed Air Filter Setup for Your System

How does Compressed air become contaminated?

A poor air supply can be caused by multiple sources. For example, compressed air can become contaminated from dirty ambient air, humidity, oils leaking from the air compressor, corroded air lines, and even from the air filter itself. Understanding the contaminants and their origin is a good starting point for shops experiencing poor air.

The majority of the contaminants found in an air system are:

  • Liquid water
  • Water vapor (humidity)
  • Oils
  • Oil vapor
  • Dust
  • Dirt
  • Aerosols

The dust and tiny particles in the ambient air around you are the same contaminants that can enter your system while it is running. Contaminants are different-sized microns and can cause varying kinds of damage depending on their form.

Compressed air can also become contaminated from oils within the air compressor, corroded air pipes, and poorly maintained air filters.

Compressed air filters pull out the bulky contaminants - like dust particles, particulates, oils, and liquid water - to prevent equipment damage and maintain air system performance.

What are inline air filters used to remove?

Inline air filters for air compressors effectively remove liquid water, oils, oil vapors, dust, dirt, aerosols and other bulky particulates. There are three types of air filters designed to remove certain contaminants:

  1. Water separators
  2. Oil Coalescing filters
  3. Activated Carbon Filters

1. Water Separators

Water separators are designed to remove large particulates and liquid water.

2. Oil Coalescing filters

Oil coalescing filters pull out oil vapors, small and fine particulates, and bulk oils from the air stream.

3. Activated Carbon filters

Activated carbon filters eliminate odors, tastes, and remove aerosols from the air flow.

How do inline Air filters work?

Each of the three filters - oil coalescing, water separators, and activated carbon - are designed to target specific kinds of contaminants. To get the clean, dry air needed for your application it may require one, two, or even three air filters. This is dependent on which contaminants should be filtered out for your system to work the way it's intended.

These filters work by removing contaminants at a specific micron size: microns are particles that cannot be seen by the human eye. Depending on the amount of air filters installed on a system, the contaminants of different micron sizes filtered out can help the air become clean and dry, or just clean. There are ISO regulations that detail the class, particle sizes, and the pressure they can withstand. This is important to refer to when choosing the right compressed air filter for you.

What is considered optimal air quality?

Air quality requirements are different for every system. There isn't a one-size-fits-all solution when it comes to filtration for equipment - air quality requirements are different for every system. The way to find the filtration required for your air compressor system, is by reading the fine print on the machine and consider the application it is being used for.

There's also a set of standard ISO -05 regulations required for some industries.

It's important to know the filtration needed for specific air systems so they operate at their highest efficiency and do not dysfunction prematurely from not having the right inline air filter.

Download our air system schematic to understand how each air filter pulls out contaminants and how they pair with the most common air dryers.

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For more information, please visit hydraulic driven air compressors.

 

choosing the right Inline Compressed Air Filter setup for your system

There are a few considerations to make before purchasing an inline compressed air filter package:

  1. The specific air requirements for your machine or application
  2. The ISO requirements of your system or industry
  3. The desired outcome of the product or process
  4. Other air treatments in place, such as drains, dryers and other filters

We recommend some initial investigation of your compressed air needs and cleanliness goals. Here's a guided checklist to get started on selecting the right inline compressed air filter:

  • Refer to the list above to determine the air cleanliness goals and needs for your system.
  • From there, determine the air demand of your system (10 CFM, 25 CFM , 50 CFM etc..) so the filters can be sized properly. Note: Purchasing larger filters does not mean cleaner air, they will only add cost to your operations.
  • Finally, make sure to choose an air filter that is of higher quality and fits your maintenance schedule. Investing in cheaper products will only add headaches to your operations as they need to be replaced more often.

Ensuring Optimal Performance with the Right Inline Compressed Air Filter

Selecting the right inline compressed air filter is a crucial step towards ensuring the efficiency and longevity of your pneumatic tools and applications. As we’ve explored, understanding the variety of contaminants in your air supply and the specific requirements of your system is fundamental. Inline air filters, ranging from water separators to oil coalescing filters and activated carbon filters, each play a distinct role in purifying your air supply.

Remember, the key to achieving optimal air quality lies not just in selecting the right filter type, but also in considering factors such as your system’s specific air requirements, ISO standards, and the desired outcome of your product or process. It’s not a one-size-fits-all situation; each system requires a unique combination of filters to meet its specific needs.

In conclusion, we recommend conducting a thorough assessment of your compressed air needs and cleanliness goals, followed by consulting with a compressed air professional. This approach ensures that you invest in a high-quality, appropriately sized filter setup that aligns with your maintenance schedule, leading to enhanced system performance and reduced operational costs.

What You Need to Know When Selecting the Compressed Air Filter?

Compressed air is not fundamentally clean, like the ambient environment from which it is pulled. The air in your compressor system contains a range of particles, aerosols, and vapors that can taint end processes and products while also harming machinery and other equipment. Here’s where compressed air filters come in!

Compressed air filtration is an essential component of your compressed air system.  Installing and maintaining the appropriate compressed air filters helps assure a continuous supply of clean air to your operations and reduces pressure drop. An industrial air compressor would need intake filters to remove impurities from entering air and an inline filter to remove particles, oil carryover, residual moisture, and smells from released compressed air. 

If you have an oil-flooded rotary screw, rotary vane, or reciprocating compressor, you will most certainly require many stages of compressed air filtration. Follow these instructions to choose the best air compressor filters for your system.

Things to Know Before You Choose a Compressed Air Filter

Filtration Efficiency

The filtration efficiency of a compressor air filter is measured by its Minimum Efficiency Reporting Value (MERV). The higher the MERV rating, the more efficient the filter is at capturing particles.

Airflow

The airflow rate is the amount of air that passes through the filter in a given period. It is important to choose a filter that can handle the required airflow rate for your compressed air system.

Pressure Drop

The pressure drop is the drop in air pressure across the filter. A high-pressure drop can negatively impact the efficiency of your compressed air filter.

Environmental Factors

Consider the environmental factors of your compressed air system, including temperature, humidity, and the presence of oil or water in the air.

Which Filter Is Right for My Air Compressor?

Different applications need different levels of filtration, so you must thoroughly understand your application before selecting the appropriate type of filter for your compressed air system.  

You should also consider whether oil can damage your process or whether any oil can still be present in the air. If your application is oil-sensitive, adding an inline coalescing filter can help reduce the amount of harmful oil that comes into contact with your end use. 

Consider how vital energy efficiency is for your facility! Low energy use means low electricity costs, and who doesn’t appreciate that?  High-efficiency filters may provide exceptionally clean air (removing pollutants smaller than 0.01 microns) while reducing pressure drop.

When should I replace my compressed air filter?

When to change a filter is determined by factors such as the hours of operation of your air compressor and the needed quality of compressed air; pressure drop can also signal that a filter needs to be replaced. Consider these four questions before deciding whether to replace a compressed air filter:

  • Has the manufacturer’s service life expired?
  • Has an air audit indicated that the air quality is below acceptable standards?
  • Is the pressure drop above tolerable levels?
  • Do pressure dips reach the manufacturer’s change point?

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