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Compressed Air Filters Filtered by Type

compressed air filter


The air around us is filled with millions of little particles that are floating around in harmless quantities to humans. This low quantity allows us to breathe the air and for our lungs to filter out the gunk through our lungs properly. The air in its normal state does not cause any problems, but the compressed air in your compressed air system does not exist in this same state.

Every cubic foot of ambient air that enters the compressor contains millions of particles from water and oil to heavy metals like lead and mercury. These particles are forced into a small space under immense pressure; naturally, these particles will start to collect and form pockets of these different particulates.

When these pockets form, it can cause the oxidation of the pipes, pressure drop, or even hamper the flow of compressed air. In order to have a healthy compressed air system with minimal machine downtime and reduced expenses, you will need to have the proper compressed air filter or filters put in place. Having the right compressed air filter in place, it reduces the wear and tear on your equipment.

When you have a compressed air filter in place, it effectively removes the particulates or condensate, depending on the style of the filter. The filter elements can be different sizes and styles to fit your compressed air system best. Please keep in mind that these filters are functioning properly and are the key to maintaining dry compressed air. Unkempt filter elements can get clogged and cause pressure drops, ruining the effectiveness of your air compressor.

The materials that need to be removed from compressed air fall into one of two categories: Condensate, which is composed mostly of water and oil, and then particulate, which refers to most of the dry contaminants like dust, dirt, and heavy metals that are present in compressed air. Just like the materials, the filter elements are constructed to remove specific types of contaminants, either particulate or condensate treatment.


What Compressed Air Filters Filter

The majority of condensed materials that are removed from compressed air consists of water and oil, which is removed by coalescing filters. The rest, the particulates, are picked up by a particulate filter, allowing water and air to pass through more easily due to the focus on the little particles flowing around. The three main things that need to be removed and why:


Solid Particles

These particulates come from the ambient air around us. The particles can cause rusting and oxidation in your system and can be introduced into the air stream because of it. In addition, having particulates present in the airstream can cause equipment to malfunction, tool failure, and contaminate products.


Condensed Water Droplets

Just as the name indicates, water condenses when the air is compressed. Those molecules end up grouping and are combined under pressure. This water can oxidize the pipes and equipment, ruin paint, and harm your final products. 

Condensation is a guarantee in compressed air, not a potential risk. When you compress air, you will also have extra water being created. It is essential to have the right compressed air filter and treatment equipment in place to prevent this moisture from causing problems


Liquid Oil and Vapors

Oil in liquid and vapor form is introduced into the air stream through the naturally occurring oil particles and the lubricant in a compressor. Unless the machine has been labeled as Oil-Free, the compressor will use oil as a lubricant to help remove heat from the air. As you’d expect, this causes some of the oil to mix with the air while it is hot and under pressure.

This oil needs to be removed for the same reasons as condensed water, especially in applications that work with food and pharmaceuticals. These industries have stringent standards due to their products being consumed by customers. So, if you didn’t know, you should not be ingesting oil in any way.


Tell Me About The Types of Compressed Air Filters

When it comes to compressed air filters, which can also be referred to as “in-line” due to their location in the compressed air system, although there are only three main types of material that need to be removed from compressed air systems, there are a few categories for filters to fall into due to specific



These filters are:

  • Centrifugal Separators 
  • Oil Separators
  • Water Separators
  • Air-Oil Separators
  • Demisters


Now a few of these categories sound similar, like what is the difference between a demister and a water separator? Aren’t they removing the same thing? By the names, they both remove water particles from the air stream, so why are there two different versions of this equipment?

The difference is in the details when it comes to filters. Most can remove similar particulates and condensate material, while others are more application specific. So rather than trying to explain what category each type of compressed air filter falls into, let’s look at the kinds of filters individually and see why you might want to include different styles in your compressed air system.


General Purpose Filters

These filters can be seen in almost every compressed air system due to the flexibility of these filters. These filters can remove liquids and solids from the air stream in general industrial applications. They grab most of the material out of the air but not to the level that some other filters can.

These filters are the go-to of compressed air filters. They get what you need and have simple maintenance routines to keep them running smoothly. So, whether you need particulates or condensate removed, general-purpose filters will give you the quality air you need.


Coalescing Filters

The general-purpose filters may work for many, but they are different from the correct answer for every application or the proper treatment for your condensate. Sometimes, applications require more oil to be removed from their airstream, or they need help with additional moisture present. 

These filters are constructed to attract moisture and oil from the air. The nature of the fibers causes the water and oil to fuse or merge with the other particles present. By trapping them in the fibers it can then allow the air to continue passing through while the water and oil stay behind. After enough of the specific material is present, the moisture will then drop down to the bottom of the filter.

Coalescing filters traditionally come after a general purpose particulate filter but before the dryer. This allows for the bigger particles to be removed before the air makes it to the coalescing filter which would be easily clogged by these larger particles. This combination provides the best possible removal of condensate and particulates prior to the dryer so that the dryer can work as expected without being overwhelmed.


Activated Carbon Filters

Some people need air that is so clean that it is better than the ambient air around us. Their process requires air that has nothing in it but clean high quality compressed air. There can be no oil, particulates, or even odor in the air stream. When this is the case, a little extra filtration is necessary.

In order to achieve that level of filtration, an additional compressed air filter is necessary. That is where Activated Carbon comes into play. These filters can get down to .003 Microns and are excellent at removing oil vapors and odors from the compressed air. Due to the size of activated carbon filters, they have to go at the end of your compressed air filters.

If the activated carbon is the first or even second filter in line, it can easily become clogged. The particulate and condensate filled air would become stuck and experience a drop in pressure and flow rate. Instead the activated carbon should always be the last in line to avoid any unnecessary components being present in the air.

Demisters/ Mist Eliminators

These filters are the most specific of the types that we have discussed, maybe even more so than the activated carbon filter. Mist eliminators are needed when you work in an environment with excess moisture and you have no wiggle room for moisture content. Demisters work exactly as you would expect them too.

Demisters are used to enhance the removal of liquid droplets from vapor steam. This may sound confusing but all these machines are doing is removing even more water vapor from the air stream, whether it be just before point of use or before your dryer. The chamber it passes through has either mesh or some structure that separates the heavier droplets from the rest of the flow.


If you have any questions about the sizing of these filters you can checkout the chart below.


Table 1


How Do Filters Stop Everything But The Air

Now that you have an understanding of the categories of filters and their different types of filters, let’s discuss the way that these filters actually remove the material from the air stream. The materials don’t just magically get stuck or disappear from the air, instead principles are used to guide these filters in how they remove material.

The degree of separation is often dictated by the style of filtration. The guiding principles for filtration are:

  • Direct interception
  • Inertial Impact
  • Diffusion or Brownian Movement


These are all descriptors for how the molecules are removed from the air stream and the properties of the material. Different combinations of sizing and material can determine what particles will be stopped/caught and what particles will pass through. Depending on the type of material, the filter can focus on removing moisture and oil or particulates. The space that is left between the fibers determines the size of the oil droplets or particles that will pass through without being removed.


The Levels of Compressed Air Filters

Compressed air filters are broken up into three different categories relating to the type and degree of filtration. These categories can give you insight into the actual size of the particles being removed by the respective filters.


Coarse Filtration

As the highest tier of filtration, this type of filter captures the biggest particles in the air stream. These filters can be sized anywhere from 5 to 40 microns, so making sure yours is properly sized is important.

Dust, dirt, and other particles that are flowing through the air are the number one target for this type of filtration. As the air passes through, these bigger pieces get stuck in the filter but the more emulsified water, oil, and air pass through in the gaps together. This means the air that goes through this filtration still contains oil and water above your desired quantities. 

In most applications, just having a coarse filter in place won’t be enough to have high-quality air as your final product. Due to the larger size of these filters, you are going to need a second step to come in and remove the emulsified oil, water, and air mixture that is in the pipes.


Fine Filtration

The next step in sizing for filtrating is Fine. This range of filtration can go anywhere from 1 Micron down to .01 Microns. This is typically the smallest size of filtration needed to achieve high quality air. We mentioned before just how small a micron is and how much smaller a tenth of one is, and only particles that are smaller than that will pass through.

If you have a standard operation, these two layers of  filtration should provide an adequate ppm of oil and water to achieve high quality air. Due to the smaller size of the filter elements, the bigger particles need to be removed before the air reaches these filters. If large particles are not separated out of the air, they will quickly clog up your filter, causing pressure drops and decreased airflow.

By having your fine compressed air filter set last in line, or if you have even finer compressed air filters, between these two steps. This ensures the highest quality of air for your application while maintaining the lifespan of your filter elements. 


Activated Carbon Filtration

If your application requires the highest quality compressed air, you are going to need an activated carbon compressed air filter in place. These filters get down to .003 microns, but this does cause a predictable pressure drop; however, if you need this level of filtration that is a simple price to pay.

Activated Carbon is used to remove oil vapors and gasses that are still present in the air after going through the previous steps of filtration. Facilities that make medications, food, or breathing air need this level of quality control because their final products are being consumed by humans with a desired effect that water or oil could ruin.

Filtration of this caliber is the best available. Nothing else gets as fine as these filters and that’s because most operations don’t need air that clean to power their tools, but when you do these filters get the job done. Just like with fine compressed air filters, ordering and sizing your filters correctly is vital to the success of your system.


Filter Your Options Finely


Filters are not an option but a necessity for your compressed air system. Without having these in place your system will fail and you could be wasting a lot of money running a system like this. The air coming off will be extremely hot and laden with water and oil, resulting in a wonderful mess of moisture and air spraying out. Obviously this is not an ideal set up for your system. 

You want to size your system and make sure that your measurements line up and make sense for your situation. Depending on your application, the level of filtration required will vary by application. Some situations might require a 5 micron particulate filter in front of a high temperature refrigerant dryer and a 1 micron coalescing after. 

While they are using that set up, a competitor might be using a particulate and coalescing in front of their desiccant and a .01 micron particulate filter after their dryer to catch the desiccant dust. There is no 100% right answer to setting up your compressed air system, but there are situations where different equipment is better. 

So make sure you are aware of any environmental factors that could affect your compressors performance when you are sizing your equipment. Humidity and extreme temperatures can both cause problems and so does variability. Having consistency and being aware of all the factors is the best way to make sure you are getting the most out of your filters.

And that is all there really is to getting your own filters in place and figuring out what kinds you need. So remember particulate first and big to small and you will be good to go.


Wanting To Buy?

If you are in need of filters, you found yourself in the right place. Warthog Air Compressor Store is home to the best of the best in compressed air filters. With brands like Atlas Copco, Nano Purification, and more available, alongside our wide selection of filter elements, Warthog is the home to keep your air clean.


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