How to Select the Suitable Air Filter for Air Compressors

Compressed air is not inherently clean. Similar to the ambient environment, the air inside a compressor system contains various particles, aerosols and vapors. 

These contaminants can pollute end processes and products, and cause damage to machinery and other equipment.

This is where compressed air filters come into play. A robust filtration system improves compressed air quality and enhances system efficiency simultaneously. 

The quantity and type of filters required for an air compressor depend on the air quality demanded by your application or process. 

Below we introduce different filter types and key considerations to help you select the proper filters for your compressor system.

Types of Compressed Air Filters

First, what is a compressed air filter? Simply put, it is auxiliary compressed air equipment that removes unwanted and potentially harmful contaminants from compressed air. 

As mentioned above, such contaminants include aerosols, solid particles and vapors.

Particulates refer to tiny solid particles such as dust, dirt, metal particles generated by pipeline corrosion and pollen. Aerosols are fine liquid droplets (oil and/or water, depending on compressor types), 

while vapors are liquids converted into gaseous state.

Although all filters ultimately achieve the same goal — contaminant removal, the three main categories operate by different mechanisms.
Compressed air filters fall into three types: coalescing filters, vapor removal filters and dry particulate filters.
Coalescing Filters

Coalescing filters remove water, oil and aerosols from air and prevent contaminants from re-entering the airflow. These filters can also trap solid particulates within the filter media. 

However, failure to replace them regularly will lead to rising pressure drop.

Coalescing filters deliver excellent contaminant removal performance, reducing particulate concentration down to 0.1 μm and liquid concentration to 0.01 ppm.
Vapor Removal Filters
Vapor removal filters operate based on adsorption. They usually adopt granular activated carbon, carbon cloth or carbon paper to remove lubricant oil vapors.
Vapor removal filters work ideally downstream of coalescing filters, as they capture and eliminate gaseous lubricants that pass through coalescing filters.
Dry Particulate Filters
Dry particulate filters are generally installed after adsorption dryers to trap desiccant particles. Their working mechanism is similar to coalescing filters.
Now that you understand air compressor filter categories, how do you confirm which filter fits your existing compressor? Is it necessary to replace the current filters?
Which Filter Is Suitable for Your Air Compressor?

Not all compressed air applications are identical. Different applications require different filtration grades. Therefore, to select the correct filter type for your compressor system, 

you need a thorough understanding of your working process.

For instance, if compressed air is used for process power in pharmaceutical, food and beverage industries, you will most likely require higher air quality compared with scenarios where compressed air drives pneumatic tools or inflates tires.

Additionally, evaluate the importance of energy efficiency for your facilities. Lower energy consumption means reduced electricity bills. 

High-efficiency filters can deliver ultra-clean air (for example, removing particles smaller than 0.01 μm) while minimizing pressure drop.

When Should Compressed Air Filters Be Replaced?
The replacement cycle depends on the operating hours of the air compressor and required compressed air quality. Rising pressure drop also serves as an indicator for filter replacement.
Consider the following questions when evaluating whether to replace compressed air filter elements:
Has the service life of the filter element expired?
Does air audit data indicate air quality below acceptable limits?
Has the pressure drop exceeded the allowable range?
Has the pressure drop reached the manufacturer’s recommended changeover point?

A "Yes" answer to any of the above questions means it is time to install a new filter element. Many users choose to replace filter elements before recommended pressure drop thresholds or air quality problems emerge. 

This is because extra energy costs caused by low air pressure can far exceed the expense of new filter elements.