ISO 29463 High-Efficiency Filters and Filter Media for Airborne Particles

The "ISO 29463 High-efficiency filters and filter media for airborne particulate matter removal" standard, published by the International Organization for Standardization (ISO), consists of the following sub-sections published under the same title:

“ISO 29463-1 Part 1: Classification, performance, testing and labeling” describes the classification of filters according to their performance, as determined in accordance with other parts of this standard. This standard also provides an overview of testing procedures and specifies general requirements for the evaluation and labeling of filters and the documentation of test results. This standard is designed to be used in conjunction with other parts.

This standard defines 13 filter classes based on minimum efficiency in MPPS:

EPA: ISO 10 E to ISO 20 E (not fully covered, lower classes comply with other standards such as ISO 16890).
HEPA: ISO 25 H to ISO 50 H.
ULPA: ISO 55 U to ISO 75 U.

Classes are specified by a number indicating the minimum integer efficiency (e.g., ISO 40 H requires a minimum efficiency of 99,995 percent, typically expressed as 1/10th of a percent).

Common equivalencies to the EN 1822 standard:

H13 ≈ ISO 35 H (at least 99,95%)
H14 ≈ ISO 45 H (at least 99,995%)
U15 ≈ ISO 55 U (at least 99,9995 percent)

Test and performance requirements are as follows:

Filters are tested using particle counting methods with liquid or solid aerosols.
Overall efficiency and local permeability (leakage) are measured.
For higher grades (HEPA/ULPA), leak testing using screening methods is mandatory.
This standard specifies pressure drop limits and documentation requirements.
The standard “ISO 29463-2 Part 2: Aerosol generation, measuring equipment and particle counting statistics” describes the aerosol generation and measuring equipment used for testing high-efficiency filters and filter media in accordance with ISO 29463-3, ISO 29463-4 and ISO 29463-5 standards, as well as the statistical basis for particle counting with a small number of counted events. This standard is designed to be used in conjunction with the other parts.

This standard details how to produce stable test aerosols, which are typically liquid or solid. These aerosols must have a controlled particle size distribution, centered around a peak MPPS (typically 0,1–0,3 μm). Requirements include:

Homogeneous concentration over time.
Methods for monodisperse or polydisperse aerosols.
Equipment specifications for generators to ensure neutrality and stability.

The focus of this standard is to address the low particle counts that are common, particularly in ULPA filter tests where downstream particles are rare. It provides:

Statistical methods based on Poisson distribution for small event counts.
Confidence intervals and minimum counting requirements to provide reliable productivity calculations.
Guidelines for determining when counts are statistically significant, avoiding erroneous conclusions due to random variations.

This statistical rigor is vital for certifying filters with efficiencies exceeding 99,999%.

The standard “ISO 29463-3 Part 3: Testing of flat plate filter media” describes the procedure for testing the efficiency of flat plate filter media. This standard is designed to be used in conjunction with other parts.

This standard specifies a detailed method for testing flat plate specimens with a test aerosol and measuring particle penetration:

The samples are placed in a test holder with a defined test area.
Aerosol testing is performed in the upstream direction following the ISO 29463-2 standard.
Particle counters measure upstream and downstream concentrations to calculate efficiency in MPPS (typically 0,1–0,3 μm).
The pressure drop across the medium is also recorded at the nominal airflow.

This allows the natural productivity of the medium to be determined independently of any potential leaks that may occur during folding, framing, or manufacturing.

This standard applies to environments designed for HEPA (ISO 25 H to ISO 50 H) and ULPA (ISO 55 U to ISO 75 U) efficiency ratings. Environments with lower efficiency ratings may refer to other standards such as ISO 16890.

The standard “ISO 29463-4 Part 4: Test method for determining leakage of filter elements - Scanning method” describes the test procedure for the scanning method, which is considered the reference method for determining leakage of filter elements. This standard is applicable to filter classes from ISO 35 H to ISO 75 U.

This standard also defines other normative methods: oil thread leak test and photometer leak test, and solid PSL aerosol leak test, applicable to HEPA filter classes from ISO 35 H to ISO 45 H.

This standard is designed to be used in conjunction with other parts.

The screening test procedure includes the following:

Test the installed filter element with a multi-dispersion or mono-dispersion aerosol in the upstream direction (according to ISO 29463-2 standard).
Systematically scanning the downstream surface using a probe connected to a particle counter or photometer.
The probe is moved at a defined speed and over a specific distance from the filter surface along overlapping paths.
Recording local particle concentrations or penetration values.

Leaks are detected when local penetration exceeds the specified thresholds (depending on the filter class according to the ISO 29463-1 standard).

The ISO 29463-4 standard ensures that the filters produced are flawless before being installed in critical systems. Clean rooms (ISO 14644 classes) are widely used in quality assurance for pharmaceutical manufacturing, semiconductor factories, hospitals, and nuclear facilities. They prevent contamination risks by detecting leaks early and support reliable performance in vital or high-value processes.

The standard “ISO 29463-5 Part 5: Test method for filter elements” describes the test methods used to determine the efficiency of filters at the highest penetrating particle size (MPPS). It also includes test and classification guidelines for filters with MPPS values less than 0,1 μm and for filters using media containing (charged) synthetic fibers (Annex B and Annex C). This standard is intended to be used in conjunction with other parts.

This standard includes rigorous in-channel testing of the assembled filter elements:

The filter is mounted in a test duct with controlled airflow at nominal volumetric flow.
In accordance with the specifications of the ISO 29463-2 standard, a test aerosol is delivered upstream.
Upstream and downstream particle concentrations are measured using optical particle counters or condensation nucleus counters.
Efficiency is calculated over a range of particle sizes, and the minimum efficiency in MPPS determines the filter class (according to ISO 29463-1 standard).
The pressure drop is recorded simultaneously.

Unlike the flat sheet test in the ISO 29463-3 standard, this evaluates the complete filter, including folds, seals, and frame.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services compliant with the ISO 29463 standard.