Jul. 07, 2025
Particulates: Particulates in compressed air are small pieces of material like dust, dirt, and/or pollen, as well as loose metal pieces. Depending on the sensitivity of your application and or process, contact with particles can be damaging to the end product. They can also cause delays in production and quality control issues, as well as unsatisfied customers.
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Aerosols: Aerosols consist of small droplets of liquid found within a compressed air system, especially in oil-injected machines. Aerosols are created from lubricant. Therefore, oil used in the compressor can be harmful to both products and people if not treated properly.
Vapors: In a compressed air system, vapors consist of lubricants as well as any other liquid that has converted to a gas. Such vapors require a special carbon activated filter in order to be removed from the system.
Now that we have a better understanding of the contaminants above, let us take a look at what types of filtration methods are used.
There are three main mechanisms utilized in dry particulate filters to remove solid particles from compressed air. These three forces contribute to the overall efficiency of the filter.
Inertial Impaction: Inertial impaction is a process where particles that are too heavy to flow with the compressed air stream get trapped in the fiber media of compressed air. The larger the particles are, the easier it will be to separate them.
Interception: Smaller particles can follow the air stream. However, if the diameter of a particle is larger than the gap of the filter media, it will get caught by the filter media. This makes it easier to eliminate larger particles than smaller ones.
Diffusion: Diffusion happens when small particles move erratically throughout the surface, instead of following the compressed air stream. This irregular movement path is caused by the particles colliding with other gas particles, an occurrence called Brownian movement. Since the particles have a free-range of motion, it is more likely that they become intercepted and removed by the filter media. Through diffusion, separation of smaller particles is easier than separating larger ones.
Two types of filters are used to remove aerosols and vapor. Coalescing filters are utilized to remove liquids as well as some particulates, while vapor filters use adsorption to remove vapors from compressed air.
Coalescing: Coalescing filters are used to remove aerosols and particulates, but are not effective in the removal of vapors. The coalescing process consists of bringing small droplets of liquid together in order to form large droplets. As the droplets increase in size, they fall from the filter into a moisture trap, resulting in a cleaner and dryer compressed air stream.
Adsorption: Adsorption is a chemical process used to remove gaseous lubricants or vapors. This process involves vapors bonding with the surface of the media (adsorbent). Activated charcoal filters are commonly used since they attract oil vapor.
As the oil vapor covers the surface of the activated charcoal over time, it is essential to change the filter before it becomes saturated. If not, this would lead to a breakthrough of the oil into the air system.
It is also necessary to use a dust filter after the activated charcoal filter. This is because small charcoal particles could break out and enter the air stream.
To assess the potential damage oil can cause to your compressed air system, it's important to understand your equipment and basic industry requirements. If your industry has strict health codes and or your equipment is sensitive to oil / vapor exposure, it is crucial to use proper filtration.
Let’s take a closer look at lubricants and understand the effects they can have on your end product. Similar to particulates,lubricants can enter your compressed air system from ambient air as well as from the compressor itself. Facility operations, like a motor exhaust, release hydrocarbons like oil aerosols into the ambient air, which can compromise air quality and cause equipment failure.
Oil injected air compressors will also release lubricants into the compressed air system, resulting in increased operational and maintenance costs. Industries such as electronics and semiconductor are especially exposed to lubricant contamination, which can result in product loss, missed deadlines and unsatisfied customers.
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