Understanding Air Quality: The ABC’s and 1‑2‑3s of ISO Air Quality Classes

Why the quality of compressed air matters — and how to determine what your system needs

Whether you’re running a manufacturing line, operating pneumatic tools, or relying on compressed air in process applications, not all compressed air is created equal. Many people assume “clean air” just means air with nothing visible in it. In reality, compressed air quality is defined by international standards — and choosing the right quality level can protect your products, equipment, and costs.

At Peerless Energy Systems, we help customers understand how these air quality standards impact their systems. Let’s walk through the essentials of compressed air quality — from the A, B, C’s to the practical 1‑2‑3 steps that simplify application.

What Are Air Quality Classes?

ISO 8573‑1 is the global standard that defines compressed air purity based on three key contaminants:

A — Solid ParticlesThis measures how many particles — like dust, rust, or other solids — are in the air stream. The standard separates allowable particles by size and counts. Cleaner air has fewer particles of smaller size.

B — Moisture (Pressure Dew Point)Moisture in compressed air can lead to corrosion, water hammer, and degraded tool performance. The lower the pressure dew point (how cold the air must be before water condenses), the drier the air.

C — Oil (Including Vapor)Oil in compressed air can damage pneumatic tools, contaminate products, and foul air‑operated instruments. This category measures both oil aerosols and vapors.

Air quality is expressed as a three‑part code (for example, ISO 8573‑1 1.4.1), with each number representing the class of solids, moisture, and oil in the air.

How to Think About Air Quality: Just Like ABCs + 1‑2‑3

It’s one thing to know what the categories are — but how do you decide what your compressed air needs?

Sullair breaks it down into three simple steps:

1. Identify Your Compressed Air Requirements

Start broad: what is your air used for?

• Are you producing products that come into direct contact with the air (like food, beverages, or medical devices)?

• Do sensitive instruments or gauges run on that air?

These questions help determine how strict your air quality needs to be — especially for particles and oil.

2. Pinpoint Specific Needs in Your System

Some compressed air system components or tools have their own sensitivities:

• Moisture can cause corrosion or tool damage.

• Particulates can wear pneumatic devices prematurely.

• Oil can contaminate processes or products.

Understanding these specifics helps you choose the right quality class.

3. Choose the Necessary Air Treatment Solutions

To meet your target air quality, you may need one or more treatment components such as:

• Air Dryers — reduce moisture

• Filters & Mist Eliminators — remove particles and oil

• Oil‑free compressors — necessary for the highest purity classes

Selecting the right combination ensures your compressed air meets the ISO class your operation demands.

Why This Matters

Getting air quality right isn’t just about compliance — it’s about reliability, efficiency, and protecting your investment. Poor air quality can lead to:

• Increased equipment wear

• Downtime

• Product contamination

• Unexpected maintenance costs

Whether you’re specifying a new compressor system or optimizing an existing one, understanding air quality classes ensures you get air that matches your application — not just air that seems clean.

If you’d like help choosing the right air quality class for your facility or exploring air treatment solutions, contact the experts at Peerless Energy Systems. We tailor compressed air systems to your exact needs — from efficient compressors to dryers, filters, and beyond.