Compressed air runs through countless facilities: powering equipment, contacting products, and keeping processes moving.
But not all compressed air is clean. Contaminants like particles, moisture, and oil can compromise product quality, trigger failed audits, and put end users at risk.
ISO 8573 defines exactly what “clean” means for compressed air systems. Understanding this standard is essential for many industries.
Understanding ISO 8573 Standards
ISO 8573 is the internationally recognized standard for compressed air quality. It defines acceptable contamination levels across three categories: solid particles, moisture, and oil.
Facilities that use compressed air for manufacturing, processing, or product applications rely on this standard to verify their air supply is safe and controlled.
The International Organization for Standardization published this standard. It’s widely adopted across industries, including pharmaceuticals, food and beverage, medical device manufacturing, and electronics.
Put simply, it gives facilities a common language for specifying, testing, and documenting compressed air quality.
Understanding ISO 8573-1 Purity Classes
ISO 8573-1 is the first and most referenced part of the standard. It assigns purity classes to compressed air based on three contaminant categories: solid particles, moisture, and oil.
Each category is rated independently. This gives facilities a precise picture of their air quality across all three dimensions.
The classes run from Class 0 to Class 9. Class 0 is the most stringent and is defined by the equipment manufacturer based on application requirements. Class 1 sets tight measurable limits, and the numbers climb as allowable contamination increases.
Particle, Moisture, and Oil Classifications
Here’s how each contaminant type is classified:
- Solid particles are rated by size and concentration. Class 1 permits particles no larger than 0.1 microns at very low counts.
- Moisture is measured by pressure dew point. Class 1 requires a dew point of -70°C (-94°F), making it suitable for the most sensitive applications.
- Oil covers both aerosols and vapor. Class 1 limits total oil content to 0.01 mg/m³.
How to Read ISO 8573 Purity Ratings
A complete ISO 8573-1 air quality rating is written as three numbers: one for each contaminant class.
For example, a rating of 1.2.1 means Class 1 for particles, Class 2 for moisture, and Class 1 for oil. Each number reflects the acceptable contamination threshold for that category.
Different applications require different combinations, which is why understanding the full rating matters more than focusing on a single class.
Why ISO 8573 Compliance Matters
Compressed air contacts products, packaging, and processing environments at nearly every stage of production.
When that air falls outside the required purity class, the consequences aren’t only a failed test result. Contaminated air can compromise batches, damage equipment, and expose facilities to serious regulatory risk.
As such, the industries with the most to lose are also the ones with the strictest requirements. Here’s a quick look at each:
Pharmaceutical and Biotech Applications
In pharmaceutical and biotech manufacturing, compressed air is classified as a critical utility. It comes into direct contact with drug products, active ingredients, and sterile surfaces. Contamination at any point in that process can invalidate an entire production run.
Regulatory bodies, including the FDA and EMA, expect facilities to define, validate, and document their compressed air quality against a recognized standard. ISO 8573 provides that framework.
Without it, facilities have no defensible basis for the air quality claims they make during audits.
Medical Device Manufacturing Requirements
Medical device manufacturing carries similar stakes. Compressed air is used in assembly, cleaning, and packaging processes where particulate or oil contamination can affect device performance and patient safety.
ISO 8573 compliance gives manufacturers a documented standard to reference during FDA inspections and ISO 13485 audits. It moves air quality from an assumption into a verified, repeatable specification.
Food, Beverage, and Cleanroom Standards
In food and beverage production, compressed air often contacts the product directly. A single contamination event can trigger a recall, a facility shutdown, or worse.
Cleanroom environments face similar pressure. Particle counts, moisture levels, and oil content must stay within defined limits to protect both the process and the end user.
How Facilities Achieve ISO 8573 Compliance
Meeting ISO 8573 requirements starts with the right compressed air equipment. As a result, most facilities invest in a combination of filtration, drying, and purification systems working together rather than relying on any single solution.
Air Filtration, Drying, and Purification Systems
Coalescing filters remove liquid aerosols and solid particles from the air stream. For oil vapor, activated carbon filters are installed downstream to absorb hydrocarbon traces that coalescing filters can’t capture.
Together, these two filtration stages address the particle and oil classifications in ISO 8573-1.
Moisture is handled separately. Refrigerant dryers work well for moderate dew point requirements, but achieving Class 1 or Class 2 moisture ratings requires desiccant dryers.
These use an adsorptive medium to bring pressure dew points down to -40°C or lower. For the most sensitive applications, dew points as low as -70°C are required.
The combination of the right dryer technology and quality filters determines which purity class a system can reliably achieve and maintain.
Validation, Testing, and Documentation
Installing the right equipment is only the first step. Further, facilities must validate that the system performs as specified under real operating conditions. That means testing compressed air at point of use, not just at the compressor outlet.
ISO 8573 Parts 2 through 9 define the testing methods for each contaminant type. Accredited testing against these methods produces results that hold up during regulatory audits.
Additionally, documentation matters as much as the results themselves. Auditors expect to see a clear record of testing frequency, methods used, results, and any corrective actions taken.
Common Compliance Mistakes to Avoid
Several avoidable mistakes put otherwise well-equipped facilities out of compliance:
- Testing at the compressor outlet rather than the point of use gives an incomplete picture of actual air quality
- Skipping revalidation after equipment repairs or system changes
- Relying on oil-free compressors alone without addressing moisture and particulate contamination
- Treating compressed air testing as a one-time exercise rather than an ongoing program
What Happens When a System Fails Compliance?
You can’t always tell when there’s a compliance failure. In many cases, contaminated compressed air moves through a facility undetected until a product test fails, an audit finds a gap, or a downstream issue forces an investigation. By that point, the damage is already done.
Product Quality and Audit Risks
When compressed air falls outside its specified purity class, every process that air touches becomes suspect. For pharmaceutical facilities, that can mean invalidated batches and compromised sterile environments.
For food and beverage operations, for example, it can trigger product recalls and facility shutdowns. Alternatively, for medical device manufacturers, it raises questions about product safety that regulators won’t overlook.
As a result, a single compliance failure rarely stays contained. Auditors investigating one gap will examine the broader quality system around it. If testing records are incomplete, validation data is outdated, or corrective action history is missing, the scope of findings expands quickly.
Corrective Actions and Revalidation
When a system fails compliance, facilities must act quickly and document everything.
The corrective action process typically involves identifying the contamination source, repairing or replacing the relevant compressed air equipment, and retesting at point of use before resuming normal operations.
Revalidation isn’t optional either. Rather, it’s the only way to demonstrate that the corrective action was effective and that the system is performing within its specified purity class again.
Additionally, facilities should conduct a root cause analysis to understand why the failure occurred. Without it, the same issue is likely to resurface.
As such, a well-documented corrective action report, paired with updated testing records, gives quality managers a defensible response if the failure comes up during a future audit.
How Class 1 Air Supports ISO 8573 Compliance
Achieving and maintaining ISO 8573 compliance requires more than the right equipment. It requires a service partner with the technical depth to validate your system accurately, respond when something goes wrong, and keep your documentation audit-ready at all times.
That’s what we do at Class 1 Air.
Accredited Testing, Certification, and Repair
Our technicians hold accreditations through NEBB, CETA, IEST, and the National Sanitation Foundation, and are certified to NSF-49 standards.
Additionally, our management team participates in standards writing committees within the Institute of Environmental Science and Technology. It keeps us current with the requirements that govern your facility.
New technicians also spend six months working alongside senior staff before conducting any independent work. As a result, every technician who arrives at your facility brings both formal training and real supervised field experience.
Our team carries an average of 10 years of industry experience, which means we’re equipped to handle complex systems and non-standard compliance challenges.
Rapid Response for Audits and Emergencies
We maintain the largest service team in the Midwest, which means we can mobilize quickly and get your system back within specification without extended downtime.
Further, our technicians train annually at a rigorous four-day CETA training camp covering all relevant CETA guides and USP standards, including USP 797, 800, 795, and 825. This keeps our team prepared for the specific requirements your facility operates under.
Audit Ready Reporting and Compliance Support
Our reporting is structured to meet FDA, ISO 14644, ASHRAE, and USP documentation expectations. Instead of scrambling to compile records, your team can then walk into any inspection with utmost confidence. Get a quote from us today and save yourself the headache.
Frequently Asked Questions About ISO 8573
Here are answers to the questions we hear most often:
How Often Should Compressed Air Be Tested?
Testing frequency depends on your industry, application risk level, and regulatory requirements.
Most facilities in pharmaceutical, food, and medical device environments test at least annually, with additional testing after any system changes, equipment repairs, or corrective actions.
A documented monitoring schedule is the most defensible approach during audits.
Can Oil-Free Compressors Guarantee Class 0 Air?
Not on their own. Oil-free compressors eliminate oil introduced during compression, but they can’t control moisture, solid particles, or hydrocarbon vapors drawn in through the intake.
As a result, proper filtration and drying systems are still required to achieve and verify any ISO 8573 purity class, including Class 0.
How Do I Choose the Right Purity Class?
Start with your application and work backward. Consider how directly compressed air contacts your product, what your regulatory framework requires, and what contamination risk your process can tolerate.
From there, match each contaminant category to the appropriate ISO classification. When in doubt, we can help you assess your system and determine the right specification.
