Inline compressed air filters can be complex – so we’ll start by clarifying the role of the filtration process and ensure you know the right questions to ask to select the optimal filter for your compressor!

Filtration is essential to excellent air compression functionality.

That’s because air is full of tiny particles, such as oil, water vapour, aerosols or other vapours. 

Leaving those particles in the compressed air causes contamination, which is detrimental to:

  • The integrity of manufactured products.
  • Air compression quality.
  • Tools and machinery.
  • The air compressor itself.

For example, suppose you had no compressed air filters. In that case, you’d see increasing rust, corrosion, breakdowns, equipment malfunctions – and that’s before even considering the impact of using contaminated air in a production facility!

Now, we’ll explore further how compressed air filters work in compression equipment.


What Standards of Filtration Do Compressed Air Filters Provide?

Ok, so given the vast number of processes, applications and industries using air compression, it’s vital to consider how clean your air needs to be – there isn’t a one-size-fits-all answer here!

Delicate production, say in pharmaceutical manufacture, will doubtless have higher filtration demands than pneumatic machinery on a construction site.

In the latter, you might opt for a dry particulate filter. That would deliver filtration down to about 0.01 microns.

However, if you’re working in a production process where complete oil vapour elimination is required for OSHA approval, you’d be better off with a charcoal activated filter.

The other factor isn’t about the required output – it’s about the quality of the ambient air being sucked into the compressor through the intake valve.

To better grasp that, we’ll explain the three principle contaminants found in compressed air.


What Contaminants Do Compressed Air Filters Remove?

Here are those three contaminants you need to remove:

  1. Particulates
  2. Aerosols
  3. Vapour

Particulates are solid materials, but often microscopic – think pollen or dust.

Industrial workshops will often also have tiny metal particles in the air, a by-product of corrosion in pipes.

Aerosols are also tiny – they are microscopic liquid droplets that are typical in an oil-injected compressor.

Lubricants create aerosols, so it’s crucial to treat the compressed air to ensure the oil used in the compressor isn’t causing problems.

Finally, vapours include liquids such as water, and other lubricants, which are converted to gas. As a result, they often need to be removed with special carbon-activated filters.


How Do Compressed Air Filters Remove Dry Particulates?

Compressed air filters can have three mechanisms, all working together to filter out solid particles.

  • Inertial impaction means that fibres in the filter trap heavier particles, separating them from the air.
  • Interception also catches particles in the filter media, using smaller gaps that larger particles can’t flow through.
  • Diffusion works because small particles move erratically rather than following the stream of compressed air. The movement happens because particles collide with gas particles – and so interception and inertial impaction can’t always remove them. Therefore, diffusion separates small and large particles, improving the filter efficiency.

It’s crucial to choose compressed air filters that offer all three filtration processes.


What Filter Do I Need to Eliminate Aerosols and Vapours From Compressed Air?

Compressed air filters remove vapours from the air, with two primary filter types.

As always, the right filter for your applications depends on what sort of vapours are present in the ambient air and what type of compressor you use. 

Oil-free compressors require different filtration processes, given the separation of lubricants from the compressed air stream.


What is a Coalescing Compressed Air Filter?

A coalescing filter removes aerosols and particles – but isn’t very suited to filtering out vapours.

The process involves combining smaller droplets. As droplets become larger, they collect in a moisture trap, making the compressed air cleaner and dryer.


How Do Adsorption Air Filters Work?

An adsorption air filter uses a chemical process, removing vapours and any gaseous lubricant.

This process bonds vapours with the adsorbent media, often with activated charcoal filters. Charcoal is a good choice since it offers a broader surface area and attracts oil vapour.

The vapour covers the filter surface, so you will need to change this regularly and before saturation.

Leaving a filter unchanged can mean oil reaches the compressed air.

Dust filters are also required if using an activated charcoal filter. That is because tiny charcoal particles from the filter can break away from the filter medium and reach the airstream.


How Can I Choose the Best Compressed Air Filters?

As we’ve explained, it’s all down to the environment, air compression requirements, and the equipment you use.

Factors include:

  • Any tolerance levels, health and safety regulations, or equipment sensitivities that dictate the level of filtration needed.
  • The lubricants you use in your air compressor.
  • Surrounding operations – if there are motor exhaust hydrocarbons in the ambient air, these will need to be filtered.
  • Whether you have an oil-injected air compressor and the subsequent filtration demands.

The best way to protect your processes from unwanted contaminants is to ensure your compressed air filters are in good condition by considering regular air compressor maintenance and suited to the equipment at hand.

If you have larger issues with your air compressor than consider air compressor repair services.