DOP Test & Particle Measurement – Requirements and Documentation

In regulated environments such as the pharmaceutical industry, food production, and hospitals, documented air quality is not an option—it is a requirement. DOP test and particle measurement therefore play a key role in ensuring that ventilation and filtration systems meet applicable standards and clean air requirements.

But when is a DOP test actually required? What exactly is being tested? And why is documentation crucial for operations, compliance, and quality?

This article reviews the requirements and explains the relationship between HEPA filter testing, particle measurement, and cleanroom validation.

When is a DOP test required?

A DOP test—also known as a HEPA integrity test —is used to verify that a HEPA filter is completely airtight and filters properly. The test verifies both filtration efficiency and airtightness, which are critical in cleanrooms and other areas with stringent air quality requirements.

This requirement typically arises in connection with:

• Cleanroom validation
• GMP Compliance in the Pharmaceutical Industry
• Installation or replacement of HEPA filters
• Periodic inspections in critical production environments

In many cases, the requirements relate to ISO 14644, including ISO 14644-1, which specifies the classification and documentation of cleanrooms. This includes both HEPA integrity testing and particle measurement as part of the overall cleanroom classification.

At HRS Luftteknik, we conduct DOP tests as part of our quality assurance process for HVAC systems in facilities with high air quality requirements. You can read more about the test itself here.

What is tested in a HEPA filter test?

A HEPA filter test (DOP test) checks:

• Whether the filter is tight across its entire surface
• Whether there are leaks in the gaskets or frames
• Whether the filtration capacity meets the requirements

The test certificate serves as proof that the installation complies with current standards.

In regulated environments, it’s not just about technology—it’s about GMP documentation and traceability. Without proper documentation, the facility cannot be considered validated.

For this reason, DOP test is closely linked to both GMP validation and cleanroom validation.

Particle measurement – documentation of actual air quality

While the DOP test checks the filter's integrity, particle measurement documents the actual air quality in the room.

A particle measurement—or particle count—measures the number and size of particles in the air. The result indicates whether the installation meets the desired classification.

In practice, air quality measurements are used for:

• Cleanroom classification according to ISO 14644
• Ongoing monitoring of process environments
• Documentation related to GMP compliance
• Assessment of the need for ventilation or filtration

Particle measurement and cleanroom testing are used not only in the pharmaceutical industry, but also in:

• Food production
• Hospitals and operating rooms
• Laboratories
• Other facilities with requirements for documented clean air

At HRS Luftteknik, we perform particle measurements in both cleanrooms and other controlled environments where documentation is essential for operational reliability and quality.

The relationship between DOP test, particle measurement, and ISO 14644

To achieve full compliance in a regulated environment, a combination of the following is often required:

• HEPA Integrity Test
• Particle counting
• Cleanroom validation
• Documentation in accordance with ISO 14644

While the DOP test verifies the filter's performance, the particle measurement verifies the room's actual air quality.

In the context of cleanroom validation, these tests are key components of the overall validation package.

In some cases, the tests are supplemented with tracer gas measurements, which are used to analyze airflow and identify any leaks or inefficient airflow patterns.

The complete documentation provides an accurate picture of the plant’s operation and is essential for both quality assurance and cost-effective operation.

Why is documentation essential?

In regulated environments, documentation is not merely a formality. It is the foundation for:

• Reliability
• Quality Assurance
• Regulatory oversight
• GMP compliance

Without documented HEPA filter testing and particle measurements, companies cannot prove that their systems are functioning properly.

Certificates from DOP test and particle measurement results serve as objective documentation that the requirements are being met—and that the system can be kept in compliance with applicable standards.

At HRS Luftteknik, DOP test, particle measurement, and trace gas measurement are performed by specialists with experience in complex process environments. These tests help ensure safety, operational reliability, and economic value for our customers.

DOP test in practice – when should it be performed?

The frequency of a DOP test depends on the classification of the environment and regulatory requirements.

Typically, a DOP test is performed:

• When commissioning a new facility
• After replacing the HEPA filters
• As part of periodic inspections
• In connection with GMP validation

Particle measurement is recommended on an ongoing basis in cleanrooms to ensure consistent air quality and documented compliance.

Companies in the pharmaceutical and food production sectors, as well as hospitals, should therefore consider DOP test and particle measurement to be an integral part of their quality management.