CompAir Oil Free Screw Compressors

What ISO 8573-1 Class 0 Means in Practice

ISO 8573-1 is the international standard that defines compressed air purity classes. It covers three contaminants: particles, water and oil. Class 0 is the highest purity classification for oil content – it means the oil concentration in the compressed air is below the detection limits of the standard measurement method.

An oil-lubricated compressor with high-quality downstream filtration can achieve Class 1 air quality – very low oil content – which is sufficient for many applications. But filtration is not infallible and filter elements can saturate, bypass, or fail. Where contamination of any kind creates safety, regulatory or product quality risk, only a certified Class 0 source eliminates that risk completely. Class 0 oil-free screw compressors are suited for applications in food and beverage production, pharmaceutical manufacturing, medical environments and electronics assembly.

The CompAir D-Series is also silicone-free – a specific certification relevant to food packaging, pharmaceutical coating and other processes where silicone contamination creates its own compliance issue.

Two-Stage Design Built for Demanding Environments

The D-Series uses a two-stage airend – air is compressed in two sequential stages rather than one. This approach keeps operating temperatures lower throughout the compression process, which reduces thermal stress on components, extends airend life, and helps maintain oil-free performance over the machine’s working life when correctly specified, installed and maintained, keeping it as energy efficient as possible.

The rotor surfaces and internal compression chamber are treated with CompAir’s patented Ultracoat coating. Ultracoat prevents corrosion and maintains dimensional stability of the rotor profiles over time – critical for ensuring that the Class 0 air quality certification remains valid through the compressor’s working life, not just at the point of manufacture.

D-Series machines are rated for ambient operating temperatures up to 45°C and use stainless steel pipework on the cold side of the system, with dual-vented seals to prevent any contamination path between the mechanical and air sides.

D-Series Range Overview

The CompAir D-Series oil-free screw compressor range covers fixed speed and regulated speed models from 37 kW to 315 kW, with flow rates from 5.1 to 51.8 m³/min and pressure options from 4 to 10 bar, depending on model.

Both air-cooled and water-cooled versions are available.

D-Series RS models use hybrid permanent magnet motor technology to improve efficiency where air demand varies. CompAir states that the HPM motor has fewer components than a standard induction version and can deliver 30% or more energy savings compared with conventional compressor control in suitable applications.

Service access is designed to be straightforward, with key maintenance points accessible from the side of the machine and coolant change intervals of up to 8,000 hours, depending on model and operating conditions.

Supply, Installation and Compliance Support from Air Energy

Air Energy is a factory-authorised CompAir service partner for the D-Series range. We supply, install and maintain D-Series compressors for regulated industries across Hertfordshire, Greater London, Buckinghamshire, Bedfordshire, Essex and Cambridgeshire. Our engineers are trained on CompAir oil-free compressor systems and provide the full service documentation required for ISO 8573 compliance audits. Check out our Service Agreements to find the best package for your needs.

If you are assessing whether oil-free air compressors are the right specification for your process, call us on 01992 238 339. We can advise on purity classification requirements for your specific application and industry sector.

Speak to an Engineer

Not sure which CompAir D-Series model is right for your application?

Request a Recommendation Or call 01992 238 339 to discuss your air purity, flow and pressure requirements.

FAQs 

What does oil-free mean in a compressor?

An oil-free compressor uses no oil anywhere in the compression process. There is no oil injection for sealing, lubrication or cooling of the rotors which means there is no possible source of oil carry-over into the compressed air supply. It is distinct from an oil-injected compressor fitted with oil removal filtration, where oil is present in the system but filtered downstream. In an oil-free compressor, the risk of oil contamination is eliminated at source rather than managed after the fact.

What is ISO 8573-1 Class 0 and why does it matter?

ISO 8573-1 is the international standard for compressed air purity. It defines classes for three types of contamination: solid particles, water and oil. Class 0 is the highest purity level for oil – it means the oil content of the compressed air is undetectable by the standard test method. Class 0 certification matters because it provides a documented, auditable assurance that the air supply cannot contaminate the product or process. For food production, pharmaceutical manufacturing and medical applications, this certification is often required by regulation or by the buyer’s own quality system.

Which industries need oil-free compressed air?

The main industries that specify oil-free compressed air are food and beverage manufacturing (where compressed air contacts products or packaging), pharmaceutical production (where contamination affects product safety and regulatory compliance), medical facilities (where air quality standards are set by HTM and ISO requirements), electronics manufacturing (where oil residue damages components), and certain chemical and textile processes. In some of these sectors, Class 0 certification is a contractual requirement from the customer or a condition of site audit.

Is the CompAir D-Series silicone-free?

Yes. The CompAir D-Series is certified both oil-free and silicone-free to ISO 8573-1 Class 0 (2010). The silicone-free certification is a specific requirement in food packaging applications where silicone contamination can affect product presentation, and in pharmaceutical coating processes where silicone residue interferes with coating adhesion. If your application requires a silicone-free air supply, the D-Series meets that requirement – confirm this to your quality team with the manufacturer’s Class 0 certification.

What is the CompAir Assure warranty on the D-Series?

CompAir Assure provides extended warranty cover on D-Series compressors for up to 44,000 hours or 6 years, whichever comes first. The programme covers the airend and key components against defect, subject to the compressor being serviced by an authorised partner using genuine OEM parts at the specified intervals. Air Energy is an authorised CompAir service partner and manages Assure agreements for D-Series customers. Service documentation is maintained to support both warranty compliance and ISO 8573 audit requirements.

What size D-Series compressor do I need?

D-Series compressor selection is based on your required flow rate (m³/min or CFM) and delivery pressure (bar), your duty cycle, and whether fixed or regulated speed is more appropriate for your demand profile. The range covers 37 kW to 315 kW. Air Energy engineers will assess your process air consumption, review your existing system if applicable, and recommend the correct model – including whether fixed or regulated speed will deliver a better total cost of ownership for your specific application.

How does a two-stage oil-free air compressor differ from a single-stage?

A two-stage compressor compresses air in two sequential steps rather than one. Air is compressed in the first stage, then passed through an intercooler before being compressed again in the second stage. Two-stage compression achieves the same final pressure as single-stage but at lower temperatures throughout – reducing thermal stress on components, improving energy efficiency, and extending the life of the airend. For oil-free compressors, lower operating temperatures also help maintain rotor profile accuracy over time, which is important for sustained Class 0 performance.

Can Air Energy service an existing D-Series compressor?

Yes. Air Energy services all CompAir D-Series compressors regardless of where they were originally supplied. As an authorised CompAir service partner, our engineers are trained on the D-Series range including regulated speed models and HPM drive systems. We can take over an existing maintenance contract, assess the current condition of the compressor, and provide the full service documentation required for compliance audits.