Oil injected and oil free compressor comparison

Oil-injected compressors are widely used across industrial environments where reliability, consistent performance, and cost efficiency are key. During compression, oil is used to lubricate, seal, and cool internal components, ensuring smooth operation and extended service life.

To achieve cleaner air, coalescing filters can remove oil particles down to 0.001 mg/m³, while activated carbon filters eliminate remaining oil vapors. When these filtration stages are correctly maintained, an air purity level of ISO 8573-1 Class 1 can be reached. Regular inspection and timely filter replacement are essential to maintain this performance over time.

Benefits:

• High energy efficiency: The oil film between moving parts reduces friction and improves sealing, resulting in efficient compression and lower energy use per unit of air produced.
• Lower initial cost: Oil-injected technology has a simpler design and typically requires a smaller investment than oil-free systems.
• Proven durability: Continuous lubrication protects internal components, allowing the compressor to run for long hours under demanding conditions.
• Stable air delivery: The cooling effect of oil maintains a consistent discharge temperature and reduces the risk of overheating.
• Flexibility with filtration: When combined with coalescing and activated carbon filters, oil-injected compressors can achieve up to ISO 8573-1 Class 1 air purity, suitable for many industrial applications.

Oil-injected compressors are therefore a dependable solution for general manufacturing, metalworking, automotive, and construction sites where air quality requirements are moderate and cost control is a key consideration.

Oil-free compressors are designed to deliver clean, contamination-free compressed air without any oil in the compression process. This design is essential in industries where air purity directly affects product quality or safety.

Benefits:

• Certified clean air: Oil-free compressors can be certified to ISO 8573-1 Class 0, the highest air purity level, ensuring that no oil enters the air stream.

• Protection of product quality: The absence of oil prevents contamination of food, medicines, electronics, and other sensitive products.

• Simplified air treatment: Since no oil needs to be filtered out, the air treatment system can be smaller and more energy efficient, with lower pressure drops.

• Reduced environmental impact: Eliminating oil from the compression process avoids oil disposal and reduces the risk of waste contamination.

• Reduced filter replacements: Oil-free compressors require fewer oil-related filter changes and generally fewer filter replacements overall, resulting in less frequent maintenance.

• Regulatory compliance: Oil-free compressors meet the strictest hygiene and safety standards, such as ISO 22000 for food production or Silicon Free certification for paint, optics, and electronics industries.

   

  These features make oil-free compressors the preferred option for applications in the food and beverage, pharmaceutical, medical, and electronics sectors, where clean air is critical for safety and product integrity.

Both types provide reliable compressed air. The choice depends on your required air quality, process sensitivity, and total cost of ownership.

The quality of compressed air directly affects product integrity, process safety, and compliance with industry standards. Even a small amount of oil can damage end products, contaminate surfaces, or increase maintenance costs.

Air purity is classified according to ISO 8573-1, the global standard defining the concentration limits for particles, water, and oil in compressed air.

The ISO 8573-1 standard defines compressed air purity levels for particles, water, and oil.

Each class indicates how clean the compressed air is and determines the required type of compressor and filtration system.

This is the highest level of air purity. Compressors certified to Class 0 ensure that no oil enters the compressed air circuit, preventing contamination in sensitive applications.

Typical industries:

• Food and beverage
• Pharmaceuticals
• Medical
• Electronics
• Paper
• Chemical production.

Class 1 allows up to 0.01 mg/m³ of total oil content (including aerosols, liquid, and vapour). It can be achieved with oil-injected compressors using advanced filtration, but it is not equivalent to Class 0.

Typical industries:

• General manufacturing
• Automotive assembly
• Other environments where minor oil traces are acceptable.

Select oil-injected compressors if:

• Air purity is important but not critical to end-product contact.

• You need an efficient, lower-cost solution for heavy-duty operation.

• Filter maintenance is manageable within the production setup.

Select oil-free compressors if:

• Your application demands certified oil-free air (Class 0).

• Any risk of contamination could affect product quality or safety.

• You operate in regulated sectors such as food, pharma, or electronics.

If you are uncertain about the required purity class, consult an Atlas Copco compressed-air specialist for guidance.

Selecting between an oil-injected and an oil-free compressor depends on more factors such as energy efficiency, lifecycle cost, and maintenance intervals. If you are unsure which technology best fits your process requirements, our specialists can help you.