What Is a Particulate Filter?

A filter for particles takes out solid particles from gases or liquids. 

Some of these particles are rust, soot, or dust. The term may be familiar to you from diesel vehicles, but the same idea is also very helpful for compressed air systems. 

Learning how these filters work does more than protect equipment. It also boosts productivity – and keeps finished products consistent in quality.

What Is a Diesel Particulate Filter (DPF)?

In many newer diesel vehicles, the exhaust includes a Diesel Particulate Filter (DPF). This filter traps soot and other particles – before they can escape into the atmosphere. The filter has to stay in place and free from blockages. 

Under Euro 5 rules, a clogged or missing DPF can have some adverse effects – and furthermore, the vehicle won’t pass its MOT.

How does DPF regeneration work?

The extra soot that has built up in the filter is burned off during the DPF regeneration process.

• Passive regeneration, when the exhaust temperatures are high enough to burn the soot, passive regeneration happens on its own.
• Active regeneration, the vehicle’s engine management system turns on active regeneration. It adds more fuel to the exhaust to raise the temperature and clear the blockage.

If this process fails, a dashboard warning light will illuminate. 

This principle of capturing harmful particles to protect a system and meet compliance standards is identical to the function of filters in industrial compressed air.

What Is a Particulate Filter in a Compressed Air System?

A particulate filter – also known as a line filter – is an important part of a compressed air system. 

It is meant to get rid of solid particles in the airstream. Dust, pollen, rust, and pipe scale from the air are some of these pollutants. This function is not for environmental emissions, but to protect the “fourth utility” (compressed air) from internal contamination.

Where Do Contaminants in a Compressed Air System Come From?

Contaminants in a compressed air system come from three main places:

1. Atmospheric Air: The compressor intake draws in countless tiny particles from the surrounding air – things like dust, pollen, and microorganisms.
2. The Compressor: The compression process itself can introduce wear particles – which typically come from moving parts. Oil-lubricated models can also contribute microscopic oil aerosols.
3. The Distribution System: Rust and pipe scale produced by corrosion in air receivers and pipework escape and flow downstream.

If not properly filtered, these contaminants can circulate through the whole compressed air system – leading to component damage and potentially affecting the process’s quality or safety.

Why Is Removing Particulates Important?

To avoid damage to operations and finances, it is important to get rid of particulates. 

Unfiltered contaminants are like sandpaper, and they wear out pneumatic tools, valves, and actuators too quickly. These particles can destroy entire product batches – leaving finishes with flaws known as “fisheyes” in delicate industries like painting, food, medications, or automobiles. 

Additionally, this contamination raises operating expenses and can result in costly unscheduled downtime.

How Do Air Treatment Systems Use Different Filters?

A complete air treatment system uses a multi-stage “treatment train” where different filters target specific contaminants in sequence. 

A single particulate filter is only one part of these comprehensive air drying and filtration solutions.

Three Main Types of Compressed Air Filters

• Particulate Filters: The purpose of these dry filters is to collect solid particles such as dust and rust. To boost energy efficiency, pleated media – like the Atlas Copco PDp+ – are often used to trap particles down to 1 µm, or as small as 0.01 µm in high-efficiency models.
• Coalescing Filters: These are engineered to remove liquid contaminants, such as water and oil aerosols. They use a dense, wrapped-media design (a depth filter) to merge tiny droplets into larger ones that can be drained. An Atlas Copco DD+ Coalescing Air Filter, for example, removes both solid particles and oil aerosols, achieving an efficiency of up to 99.999% for oil aerosols.
• Activated Carbon Filters: These use adsorption on a molecular level to remove oil vapour, chemical fumes, and odours. They are always placed after a coalescing filter to prevent liquid oil from saturating the carbon media. This makes them well suited to odour-sensitive settings – like food production or pharmaceutical packaging.

What Is a Particulate Filter

How Do Filter Designs (Pleated vs. Depth) Differ?

Compressed air filters use two primary construction designs based on the contaminants they target:

1. Pleated Filters: These have a filter media (like cellulose or polyester) that is folded in an accordion-like way. This pleating greatly increases the surface area, which is perfect for catching a lot of dry, solid particles with very little pressure drop. This design is used by the Atlas Copco PDp+ series for dry dust.
2. Depth Filters: These use a thick, wrapped matrix of tightly packed fibres, like borosilicate microglass. This design makes air go through a complicated path, which is necessary for the coalescing process. This process combines tiny liquid aerosols (oil and water) into bigger droplets that gravity can pull away. This depth design is used in the Atlas Copco DDp+ series.

How Is Compressed Air Purity Measured in the UK?

ISO 8573-1 is an international standard that tells you what clean air is. 

In the UK, any system that produces oil mist must comply with COSHH and the Pressure Systems Safety Regulations 2000 (PSSR).

If the air is intended for breathing or similar specialised uses, it also needs to meet the BS EN 12021 requirement.

The table below shows how the limits on particles differ for each class. 

How Does Filter Maintenance Impact Energy Efficiency?

Air has to work harder to get through filters that have dust on them. 

When pressure drops, the compressor has to work harder – energy use can rise by as much as 8% for every bar lost.

To avoid this, replace the particulate filter yearly, after about 2,000 operating hours – or whenever the pressure drop becomes noticeable.

Regular filter changes help maintain system protection and lower power consumption.

Ensuring Correct Filtration with Search Air

If you’re unsure about your filtration setup, our engineers can help. As a Premier Distributor for Atlas Copco, Search Air provides genuine air compressor filters and separators, service kits, and AIRScan audits across Yorkshire and the East Midlands. We supply correct-spec parts and perform compressor air quality testing to verify compliance.

Frequently Asked Questions

What does a particulate filter do in a compressor?

Inside a compressor system, the particulate filter traps dry particles like dust, rust, and bits of pipe scale before they can circulate. If these aren’t removed, they can damage tools – and shorten the system’s life. 

Keeping the filter clean helps everything run smoothly. And furthermore, it reduces the chance of breakdowns which helps to keep costs down.

How often should I replace my particulate filter?

You should change a particulate filter every 2,000 hours – or once a year. You should also consider a replacement when the pressure drop across it gets too high. This is because when a filter is blocked, it wastes energy.

What is the difference between a coalescing and particulate filter?

A particulate filter uses pleated media with a large surface area to capture solid, dry particles. Tiny liquid aerosols, such as water and oil, are captured by a coalescing filter, which then condenses them into larger droplets that can be drained off. It does this by using a deep, dense-fiber media.

Which ISO class does my industry require?

This depends on your application. General manufacturing may use Class 3 or 4 for particles. High-purity applications like food, pharmaceutical, and electronics manufacturing require the most stringent standards, often ISO 8573-1 Class 1.

Keep your air clean, your system efficient, and your business compliant. Contact Search Air today to book an AIRScan audit or request a filter replacement quote.