Inline Filter Selection for Compressed Air Systems

Author: Evelyn

Jun. 30, 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.

 

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.

Contact us to discuss your requirements of hydraulic driven air compressors. Our experienced sales team can help you identify the options that best suit your needs.

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.

How Do I Select and Properly Size an Inlet Filter?

Selecting an Inlet Filter for Your Blower, Compressor, or Vacuum Pump.

The key to achieving peak output performance from your compressor, blower, vacuum pump, engine, or any other machine that moves, processes, or consumes air – is ensuring clean, unrestricted air flow at the inlet. Appropriate filtration technology is essential to optimizing and protecting your equipment and working environment, even when severe external conditions are present. A critical factor for optimizing performance from your equipment is properly selecting and sizing your filter cartridge and housing. Through selecting the correctly sized filter, your equipment will operate smoothly over a longer period of time while also avoiding costly maintenance or downtime.  Although it is always best to enlist filtration experts in the selection process, this article provides general guidelines for selecting and sizing particulate filters to protect your equipment.

Inlet filters come in many configurations and sizes.  The two main types of inlet filters include:

  • Inlet Vacuum Filters, or Inline Vacuum Filters for vacuum pumps
  • Inlet Air Filters, or Ambient Air Intake Filters for Blowers, Compressors, Fans, Engines

Selecting the appropriate filter depends on the type of equipment being protected and the conditions in which the filter will be deployed.  Gathering as much application information as possible up front, helps ensure success in the selection process. 

To properly size a filter element and housing, two basic but very important pieces of information about your equipment are required:

  • Maximum Flow capacity
  • Maximum allowable pressure differential

Using this crucial information, the appropriate sizing can be determined based on filtration media type and allowable velocity through the  media. The minimum connection for the housing connection can also be determined based on flow requirements. High velocities through your filtration media or housing connection can significantly affect filtration performance and pressure drop. Generally, slower air velocity through a media delivers higher filtration efficiency and lower pressure drop across the filter element. A properly sized filter is essential for optimizing an air system’s performance and should be considered early in your design phase for any pneumatic or vacuum system.

Polyester Media Filter Cartridge Rated at 99%+ Removal Efficiency for 5-Mircon.

The following are the key concerns in specifying the optimally sized filter for your industrial application.

#1: What are my filtration requirements? Selecting a Filter Media.

Always begin the selection process by identifying the appropriate media and filter element size based on the following requirements: filtration level, pressure drop, temperature, and chemical compatibility. Solberg manufactures air filter-cartridges using a variety of standard and specialty medias designed to meet specific requirements relating to operating conditions, type of contaminant, removal efficiency, and micron rating.

Note: Indicating an efficiency level with a specific micron requirement is essential to choosing the right media; stating the need for a “1-micron filter” is incomplete without the efficiency rating. For example, a 5-micron filter with 99% filtration efficiency is adequate for most general duty industrial applications. Follow the suggested *Air-to-Media ratios for the external environment conditions and filtration efficiency needs. 

#2: How will process contaminants affect the life of my filter? Selecting a filter-cartridge size.

Contaminant level and type can significantly impact the life of your filter and the level of maintenance required for your equipment. As a filter stops the contaminants from entering the equipment, the filter element begins to load or clog with contaminant and the pressure differential steadily increases until a terminal pressure differential is reached. At this point, the filter element must be replaced.

Solberg’s published flow rates for elements takes filter-life into consideration and provides a reasonable maintenance interval for most general-duty industrial applications. When exposed to harsh operating conditions, it is recommended to select larger filter elements with a greater surface area. Larger filter elements can significantly prolong the life of your filter and extend the maintenance intervals for your equipment.

#3: How do I determine the connection size for my filter-housing? Selecting a filter-housing size.

After selecting the appropriate filter media (#1) and element size (#2), the appropriate housing for your filter element must be determined. As a best practice, match the connection size of your filter housing to that of the equipment being protected or the pipe size of the application’s plumbing - this will help in minimizing pressure differential contributed by the filter housing. While it is acceptable to select a larger connection size, downsizing a connection which is smaller than the pipe size should be avoided.

Filter Silencer (FS Series) with hex fitting connection and carbon steel housing.

Becoming a Filtration Expert.

Understanding how flow and pressure drop influence sizing and selection is the first step to building your knowledge-base and becoming a filtration expert.  There are many other important variables that must also be considered when selecting the best filtration solution for an application’s unique operating conditions - temperature, pressure, type of contaminant, moisture level, and more. Specific requirements such as materials of construction, design codes, and installation will also significantly influence the selection process.

Sound overwhelming? Enlist the experts when you need assistance!

Solberg Filtration is a leading manufacturer in vacuum filters, filter silencers, separators, and oil mist eliminators for compressors, blowers, vacuum pumps and power generation. Feel free to contact us regarding your filter sizing concerns as well as any other technical inquiries.

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