Medical Device and IVD Manufacturing: Compressed Air Quality, Applications and Compliance Considerations

Compressed air is widely used throughout medical device and In Vitro Diagnostic (IVD) manufacturing facilities. Applications range from operating pneumatic equipment to drying components, purging fluid pathways, cleaning selected surfaces, assisting assembly, and supporting automated production processes.

However, compressed air is not inherently clean simply because it has been compressed, filtered or supplied through a dedicated utility system.

It can contain solid particles, moisture, oil aerosols, oil vapour, gaseous contaminants and microbiological contamination. Depending on the application, these contaminants may affect product cleanliness, material properties, fluid flow, manufacturing consistency, or the microbiological condition of a product-contact surface.

ISO 8573-1, Compressed air — Part 1: Contaminants and purity classes, provides a framework for specifying compressed-air purity according to three principal contaminant categories: particles, water and oil. It also addresses gaseous and microbiological contaminants as additional considerations.

For medical device and IVD manufacturers, the critical question is not simply which compressed-air class is the cleanest. It is:

What level of compressed-air purity is required for each application, how should that requirement be designated, and how can the manufacturer demonstrate that the required quality is consistently achieved at the point of use?

This article explains how to apply the classification system and develop appropriate requirements for product-contact applications, cleanrooms, sterile manufacturing environments, and IVD processes.

Understanding the ISO 8573-1:2010 classification system

ISO 8573-1:2010 establishes purity classes for three principal contaminant categories.

The general designation is:

ISO 8573-1:2010 [A:B]

Where:

• A is the particle purity class.
• B is the water purity class.
• C is the oil purity class.

Each number represents a separate requirement. The three numbers are not an average, a single cleanliness score, or a cleanroom grade.

For example:

ISO 8573-1:2010 [1:2:1]

This means:

• Particle purity: Class 1.
• Water purity: Class 2.
• Oil purity: Class 1.

The classification must be interpreted against the applicable limits in the standard. A requirement should also identify the measurement location and any additional parameters necessary for the intended process.

How are the purity classes determined?

Particle purity classes

Particle classification considers the concentration of solid particles within specified particle-size ranges.

For classes 1 to 5, the particle-number limits in ISO 8573-1:2010 are expressed in terms of particles per cubic metre.

The following table summarizes the particle-number criteria for these classes.

Particle concentration limits are per cubic metre of compressed air. “Not specified” means that the corresponding size range is not assigned a limit by that class criterion; it does not mean that particles are absent.

Classes 6 and 7 use mass-concentration criteria rather than the particle-number criteria shown above. They should be interpreted using the relevant provisions of the standard.

Application to medical devices and IVDs

Particle classification becomes particularly important when compressed air is used to:

• Blow or dry components before assembly.
• Purge internal device passages or IVD fluidic channels.
• Contact exposed product-contact surfaces.
• Operate in proximity to exposed sterile components.
• Support precision assembly, dispensing or sensitive analytical processes.

The required particle class should reflect the consequence of contamination. For example, a particle introduced into a narrow IVD fluid pathway may affect flow or reagent delivery, while a particle deposited on a component intended for a critical bonding operation may affect bond integrity.

The particle class alone does not establish that a component is microbiologically clean or that its surface is suitable for its intended use.

Water purity classes

Water classification considers pressure dew point and, for the relevant classes, liquid-water content.

For classes 1 to 6, the principal pressure-dew-point criteria are:

Classes 7 to 9 address liquid-water concentration, while Class X represents contamination exceeding the Class 9 limit or otherwise requiring the specified X-class designation.

Application to medical devices and IVDs

Water requirements should be evaluated where compressed air is used for:

• Drying components or assemblies.
• Purging internal passages.
• Supporting processes sensitive to moisture.
• Operating pneumatic equipment where condensation could affect performance.
• Supplying air to locations where moisture could contribute to corrosion or contamination.

A low pressure dew point does not establish that liquid water, particles, oil or microorganisms are absent under every operating condition. These are separate aspects of the specification and system performance.

Oil purity classes

Oil classification addresses total oil content within the scope of the standard, including the applicable liquid, aerosol and vapour forms.

Class 0 is a specially defined class requiring a documented contamination limit that is more stringent than Class 1. It does not mean zero oil or zero contamination.

Class 0 should not be specified without defining the agreed maximum allowable concentration and the method by which compliance will be demonstrated.

Application to medical devices and IVDs

Oil contamination may be relevant when compressed air contacts:

• Surfaces intended for bonding or coating.
• Components that will subsequently contact medicines, biological materials, reagents or patient samples.
• Internal fluid pathways.
• Components intended for sterilization or other controlled processing.
• Sensitive optical, analytical or precision assemblies.

An oil-free compressor may reduce one source of contamination, but it does not independently prove that the air delivered at the point of use meets the specified oil class.

The class limits above are a summary of ISO 8573-1:2010. Consult the full standard for the complete classification criteria, reference conditions and designation requirements.

Quick reference: ISO 8573-1:2010 compressed-air purity classes

The following consolidated table is a simplified reference view of particle, water and oil class criteria. Use the applicable clauses and tables in the full standard when establishing specifications.

Important: A dash means that the corresponding criterion is not specified in this simplified presentation; it does not mean zero contamination.

How should a manufacturer designate compressed-air purity?

A compressed-air specification should be written so that engineering, quality assurance, production and the testing laboratory can interpret the same requirement without ambiguity.

Example 1: Different classes for different contaminants

A manufacturer determines that the required specification for a particular application is:

ISO 8573-1:2010 [2:2:1]

This designates particle Class 2, water Class 2 and oil Class 1.

The manufacturer must then identify the applicable acceptance criteria, test methods, sampling location and monitoring arrangements.

This example illustrates designation only. It is not a universal recommendation for medical device or IVD production.

Example 2: Unspecified contaminant category

Where a class for one of the three principal contaminant categories is not specified, a hyphen is used.

For example:

ISO 8573-1:2010 [1:−:1]

This specifies particle Class 1 and oil Class 1, without specifying a water class.

For a medical device process, leaving a category unspecified should be a deliberate and documented decision. It should not be used merely because the corresponding parameter has not yet been assessed.

Example 3: Class 0 specification

A Class 0 designation requires a specific, documented limit more stringent than Class 1 for the relevant contaminant.

The manufacturer should state the agreed limit, unit of measurement, relevant test method and acceptance criteria. Writing “Class 0” alone is insufficient to define the actual requirement.

Example 4: Additional microbiological or gaseous requirements

The three-number designation does not communicate a viable microbial limit.

Where microbiological contamination is relevant, the specification should include a separate requirement measured using the applicable method, such as ISO 8573-7 for viable microbiological contamination.

For example, a manufacturer might specify:

• Compressed-air purity: ISO 8573-1:2010 [2:2:1].
• Viable microbiological contamination: a separately defined maximum in CFU/m³.
• Additional chemical or gaseous limits, where justified by the application.

The microbial limit must be established by the manufacturer based on the process and its risk assessment; the example does not imply a universal acceptance limit.

Applying ISO 8573-1 to medical device and IVD manufacturing areas

The purity class should be established for the intended use of the air, not assigned solely on the basis of the room classification.

The following table provides a practical starting point for application assessment.

These are assessment categories, not prescribed ISO purity classes. The manufacturer must determine the actual specification for each application.

Direct product-contact compressed air: what should be considered?

Direct-contact compressed air requires particular attention because the air may introduce contamination onto the product or into a product-contact pathway.

The term direct contact should be defined according to the actual process. It can include air that touches a component, enters a fluid pathway, or contacts a surface that will subsequently contact a patient sample, reagent or other critical material.

The following questions should be addressed.

What is the product-contact pathway?

Determine whether compressed air contacts:

• The finished device.
• An internal fluid pathway.
• A surface that will contact a patient or sample.
• A component that will subsequently be assembled into the device.
• A surface that is intended to remain clean until sterilization or packaging.

The answer determines which contamination hazards are relevant and what evidence is necessary.

Could the air introduce non-viable contaminants?

Non-viable contaminants include solid particles, liquid droplets, oil residues and other non-living material.

Depending on the application, these may cause:

• Physical blockage of a narrow passage.
• Alteration of surface properties.
• Interference with bonding or coating.
• Residues that are difficult to remove.
• Interference with the operation of a fluidic or analytical system.

The manufacturer should define appropriate particle, oil and water limits and evaluate any additional chemical contaminants that could affect the product.

Could the air introduce viable contaminants?

Viable microbial contamination is a separate consideration. Depending on the application, microorganisms introduced through compressed air may affect a product's microbiological condition or compromise a contamination-control strategy.

The required microbial limit should be justified by the intended use, product characteristics, subsequent processing and risk assessment.

For devices intended to be sterile, a validated sterilization process does not automatically make uncontrolled contamination acceptable. Residues and particles may remain, and excessive or variable bioburden may affect process control.

Where should the air be tested?

The most relevant location is generally the point where the air is used or where its quality can affect the product.

A representative sampling plan should account for:

• The condition of the main compressed-air supply.
• Downstream piping and treatment equipment.
• Point-of-use filters and connections.
• The operating conditions under which air is delivered.
• Potential contamination introduced after central treatment.

Testing at the compressor outlet alone may not establish the quality of the air reaching a critical manufacturing operation.

Compressed air used in cleanrooms and controlled environments

One of the most important distinctions for medical device and IVD manufacturers is the difference between compressed-air purity classification and cleanroom air classification.

ISO 8573-1 applies to compressed air. ISO 14644-1 addresses classification of air cleanliness in cleanrooms and associated controlled environments based on airborne particle concentration. These classifications are not interchangeable.

A cleanroom may have a defined airborne particle classification, but that classification does not automatically establish the purity of compressed air delivered through a pneumatic line.

Similarly, a compressed-air system meeting a selected ISO 8573-1 designation does not establish that the surrounding cleanroom meets its required classification.

Compressed air released inside a cleanroom

Where compressed air is released into a controlled environment, the manufacturer should assess whether the discharge could introduce particles, oil aerosols, moisture or microorganisms into the room.

The assessment should consider the discharge location, air flow, duration of use, proximity to exposed product and the potential impact on environmental controls.

The compressed-air specification and the cleanroom environmental controls should be addressed separately and then evaluated together as part of the overall contamination-control strategy.

Compressed air used near exposed sterile components

Where components are exposed before sterilization, sterile barrier formation or another critical manufacturing step, compressed-air contamination may affect the condition of the components.

The risk assessment should consider whether non-viable particles, oil residues or microorganisms could remain on the product and whether the subsequent process adequately controls the identified hazards.

A requirement for a low particle count should not be treated as proof of microbiological suitability.

Compressed air used in controlled assembly or packaging areas

Air used to actuate equipment in a packaging or assembly area may have different requirements from air blown directly onto a component or into an internal pathway.

The distinction depends on the credible contamination pathway and the impact of the air on product quality. The room's classification alone is not sufficient to determine the required ISO 8573-1 class.

Viable and non-viable contamination: two different control objectives

Medical device and IVD manufacturers should distinguish between the control of physical contaminants and the control of viable microbiological contaminants.

ISO 8573-1 does not provide a universal microbiological purity class. ISO 8573-7 specifies a method for determining viable microbiological contamination in compressed air.

A manufacturer should therefore define viable microbial acceptance criteria separately wherever microbiological contamination is a relevant risk.

Is a microbial test required for every compressed-air outlet?

Not necessarily. The need for microbial testing should be justified by the application and risk assessment.

Testing may be particularly relevant where compressed air directly contacts a product, an internal fluid pathway or a surface with critical microbiological requirements.

It may also be relevant where air is used in a process in which microbial contamination could compromise a subsequent manufacturing or sterilization step.

For general pneumatic equipment with no credible route to product contamination, routine microbial testing may not be justified. This decision should be documented rather than assumed.

8.2 Does a microbiological test replace particle testing?

No. Viable and non-viable contamination represent different quality attributes.

A system can meet a defined microbial criterion and still contain unacceptable particles, oil or moisture. Conversely, a low particle count does not prove that the air is microbiologically suitable.

Both sets of requirements should be addressed where the application requires them.

How should a manufacturer select the required class for each application?

A practical assessment should begin with the application rather than a preselected purity class.

Step 1 — Map the compressed-air users.

Identify each point of use, the equipment supplied, the manufacturing operation and whether the air contacts the product or its environment.

Step 2 — Determine the contamination pathway.

Assess whether particles, water, oil, chemicals or microorganisms could reach the product or affect a critical process characteristic.

Step 3 — Define the required attributes.

Determine which ISO 8573-1 classes are needed and whether additional limits for viable contamination, gases, chemical residues or other process-specific attributes are necessary.

Step 4 — Establish the acceptance criteria.

Document the maximum permissible levels, test methods, sampling conditions, measurement units and applicable reference conditions.

Step 5 — Establish the treatment and distribution requirements.

Select the compressor technology, dryers, filtration stages, distribution materials and point-of-use controls appropriate to the defined requirements.

Step 6 — Verify the delivered air quality.

Demonstrate compliance at representative points of use under suitable operating conditions. Use methods appropriate to each contaminant and its specified acceptance limit.

Step 7 — Maintain the approved state.

Define monitoring frequency, preventive maintenance, investigation criteria and the conditions that trigger additional testing or requalification.

This process creates a traceable connection between the intended use of compressed air, the contamination risks, the selected class and the evidence used to demonstrate compliance.

Verification and ongoing monitoring

Selecting a class does not demonstrate that the compressed-air system consistently meets that class. The manufacturer should establish appropriate verification and maintenance controls.

A verification programme may include:

• Particle measurement using the applicable test method.
• Measurement of pressure dew point or other relevant water parameters.
• Assessment of oil aerosol, vapour and total oil as applicable.
• Gaseous contaminant testing where identified as relevant.
• Viable microbiological testing where justified.
• Assessment of sampling locations and operating conditions.
• Review of test results, deviations and adverse trends.
• Reassessment following significant changes to equipment, filters, dryers, piping or points of use.

The relevant parts of the ISO 8573 series provide test methods for specific contaminant categories. The method must be appropriate for the actual parameter and the required class.

Testing should be planned so that the evidence demonstrates the air quality required by the process—not merely the performance of an individual filter or the manufacturer's nominal equipment rating.

Practical example: compressed air used to purge an IVD cartridge

Consider an IVD manufacturer that uses compressed air to purge an internal channel before cartridge assembly.

The air directly enters a pathway that will subsequently carry a reagent or patient sample. The manufacturer should assess:

• Whether particles could remain in the channel and obstruct fluid movement.
• Whether oil residues could alter the surface or affect the movement of fluid.
• Whether moisture could interfere with subsequent processing or reagent performance.
• Whether viable microorganisms or other contaminants could affect the intended use.
• Whether downstream manufacturing steps can detect or control the identified risks.

The manufacturer would then establish the required particle, water and oil classes, define additional microbial or chemical limits if necessary, and verify the air quality at the point of use.

The selected classes should be supported by documented technical justification. There is no single ISO 8573-1 designation that can be assumed suitable for every IVD cartridge or fluid pathway.

Related standards and their roles

The following standards can support the overall assessment, depending on the application.

The standards serve different purposes. Their use should be determined by the applicable requirements and the manufacturer's documented assessment.

For medical device and IVD manufacturers, ISO 8573-1:2010 provides a structured way to define compressed-air purity requirements. Its designation system enables separate requirements for particles, water and oil to be communicated and verified.

However, an ISO 8573-1 designation should not be treated as a complete contamination-control specification for every manufacturing application. Direct product contact, cleanroom discharge, exposed components, sterile device processing and IVD fluid pathways may introduce additional requirements that must be addressed through risk assessment.

Viable microbiological contamination must be considered separately from non-viable particles, and compressed-air purity must remain distinct from cleanroom classification.

The objective is to establish a justified specification for each relevant point of use, verify compliance using suitable test methods, and maintain evidence that the required quality is consistently achieved.