ASTM F91-06(2019)

Standard Practice for Testing for Leaks in the Filters Associated With Laminar Flow Clean Rooms and Clean Work Stations by Use of a Condensation Nuclei Detector

ABSTRACT
This practice covers the testing of the integrity of high-efficiency particulate air (HEPA) filters installed in laminar flow clean rooms of the ceiling to floor or wall to wall type, and laminar flow clean work stations using condensation nuclei detector. The recommended practice may be used to detect faults or voids in the filter media itself or in the joints between the filter and the room or work station structure. The preparation for testing and the procedure for the proper testing are presented in details.
SCOPE
1.1 This practice covers the testing of the integrity of high-efficiency particulate air (HEPA) filters installed in laminar flow clean rooms of the ceiling to floor or wall to wall type, and laminar flow clean work stations. The recommended practice may be used to detect faults or voids in the filter media itself or in the joints between the filter and the room or work station structure. The determination of filter media efficiency is not within the scope of this practice.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.2.1 Exception—The values given in parentheses in inch-pound units are for information only.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Jun-2019
• ICS: 13.040.30 - Workplace atmospheres
• Technical Committee: E21 - Space Simulation and Applications of Space Technology
• Drafting Committee: E21.05 - Contamination

Relations

• Replaces: ASTM F91-06(2011) - Standard Practice for Testing for Leaks in the Filters Associated With Laminar Flow Clean Rooms and Clean Work Stations by Use of a Condensation Nuclei Detector
• Effective Date: 01-Jul-2019

Overview

ASTM F91-06(2019) is the internationally recognized standard practice for testing leaks in the filters associated with laminar flow clean rooms and clean work stations using a condensation nuclei detector. Developed by ASTM International, this standard provides recommended procedures for verifying the integrity of high-efficiency particulate air (HEPA) filters. The focus is on detecting faults, leaks, or voids either in the filter media itself or at the joints between the filter and the room or work station structure. This standard is essential for organizations seeking to maintain cleanroom environments critical for contamination-sensitive processes across various industries.

Key Topics

• HEPA Filter Leak Integrity: The standard outlines a methodology for testing the integrity of installed HEPA filters, ensuring that unfiltered air does not penetrate clean room spaces.
• Condensation Nuclei Detection: It leverages the sensitivity of condensation nuclei detectors, which can identify increased particle counts that indicate the presence of leaks.
• Testing Procedure: The practice provides step-by-step guidance, including apparatus assembly, measurement protocols, scanning of filter surfaces and edges, and the interpretation of detector readings.
• Interpretation and Remedial Action: When elevated nuclei counts are detected (commonly a ten-fold increase from background), the method instructs operators on pinpointing and marking leak locations for follow-up corrective measures.
• Safety and Measurement Units: While offering detailed procedures, the standard emphasizes the user’s responsibility for safety and regulatory compliance. All measurements are specified in SI units, with inch-pound equivalents for reference.

Applications

The proper functioning of HEPA filters is essential in environments where contamination control is of utmost importance. This standard is used in:

• Pharmaceutical Manufacturing: Ensuring sterility in production areas by confirming HEPA filters are free of leaks that could compromise product safety.
• Semiconductor and Electronics Fabrication: Maintaining low particulate environments necessary for sensitive electronic device manufacturing.
• Healthcare Facilities: Protecting clean rooms and surgical environments from airborne contaminants.
• Laboratory Environments: Supporting research or production processes that require strict control of airborne particulates.

By routinely applying ASTM F91-06(2019), organizations can detect and promptly address leaks or voids that may introduce contaminants, ensuring compliance with cleanroom classification requirements and protecting critical processes.

Related Standards

Organizations using ASTM F91-06(2019) may also reference the following related standards to complement their cleanroom maintenance programs:

• ISO 14644 Series: International standards for cleanroom design, operation, and particle contamination control.
• ASTM F50: Standard practice for continuous monitoring of air cleanliness in cleanrooms.
• ASTM E2090: Standard test method for size-differentiated counting of airborne particles in cleanrooms and work stations.
• IEST-RP-CC034: Institute of Environmental Sciences and Technology’s guidance on HEPA and ULPA filter testing and certification.

Practical Value

Adhering to ASTM F91-06(2019) helps organizations:

• Maintain compliance with regulatory and industry standards for clean environments.
• Detect faults early, reducing the risk of compromised products or research outcomes.
• Protect investments in cleanroom infrastructure and critical filtering equipment.
• Ensure the ongoing reliability of HEPA filters, which play a pivotal role in contamination control strategies.

By following this standardized leak testing practice, facility managers, quality control professionals, and engineers can uphold the necessary cleanliness levels for high-stakes processes, supporting both operational integrity and product safety.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F91 − 06 (Reapproved 2019)
Standard Practice for
Testing for Leaks in the Filters Associated With Laminar
Flow Clean Rooms and Clean Work Stations by Use of a
Condensation Nuclei Detector
This standard is issued under the fixed designation F91; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.1.4 leak—a gap or void in the filter media, or in the
associated gaskets, which permits unfiltered room air to pen-
1.1 This practice covers the testing of the integrity of
etrate the clean room or clean work station.
high-efficiency particulate air (HEPA) filters installed in lami-
nar flow clean rooms of the ceiling to floor or wall to wall type,
3. Summary of Practice
and laminar flow clean work stations. The recommended
3.1 This recommended practice takes advantage of the fact
practice may be used to detect faults or voids in the filter media
that a HEPAfilter retains a high percentage of the condensation
itself or in the joints between the filter and the room or work
nuclei found in ordinary room air. In this recommended
station structure. The determination of filter media efficiency is
practice a nuclei counting apparatus is arranged to sample
not within the scope of this practice.
small areas at the filter surface and the joints at the filter edges.
1.2 The values stated in SI units are to be regarded as
The HEPA filter effluent normally shows a low nuclei count
standard. No other units of measurement are included in this
(<100 particles/cm ).When a leaking filter area is encountered,
standard.
an increase of at least ten-fold in the particle count is noticed
1.2.1 Exception—The values given in parentheses in inch-
within the 2-s response time of the nuclei counter.
pound units are for information only.
1.3 This standard does not purport to address all of the
4. Apparatus
safety concerns, if any, associated with its use. It is the
2,3
4.1 Condensation Nuclei Counter.
responsibility of the user of this standard to establish appro-
4.2 Plastic Tubing , 9.5 mm ( ⁄8 in.) in outside diameter;
priate safety, health, and environmental practices and deter-
6.5 mm ( ⁄4 in.) in inside diameter; of suitable length, not to
mine the applicability of regulatory limitations prior to use.
exceed 1.5 m (5 ft).
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
4.3 Glass Laboratory Funnel, 50 mm in outside diameter,
ization established in the Decision on Principles for the
7 mm in stem diameter, 80 mm over-all length.
Development of International Standards, Guides and Recom-
4.4 Double-Pole Single-Throw Relay, 115 V, 8 A.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
5. Preparation for Test
2. Terminology
5.1 Assemble the apparatus by slipping one end of the
plastic hose over the funnel stem, and the other end over the
2.1 Definitions:
nuclei counter input nipple.
2.1.1 condensation nuclei—particles within the size range
from 0.001 to 0.1-µm radius.
5.2 Turn on the electrical supply to the nuclei counter and
allow 30 min warm up time with the input tube sampling the
2.1.2 HEPA filter—high-efficiency particulate air filter.
effluent from a HEPA filter.
2.1.3 laminar flow—airflow in which the air confined within
the walls of a room or a smaller work station moves as an 5.3 Measure the nuclei concentration at the intake to the
isovelocity front along parallel flow lines. HEPA filter. A concentration of less than 1000 particles/cm
This practice is under the jurisdiction of ASTM Committee E21 on Space
Simulation andApplications of Space Technology and is the direct responsibility of Rich,T.A., “AContinuous Recorder for Condensation Nuclei,” Geofisica Pura
Subcommittee E21.05 on Contamination. e Applicata, Milano, Vol 50, 1961, III, pp. 46–52.
Current edition approved July 1, 2019. Published July 2019. Originally approved General Electric Co., Schenectady, NY, Model No. 112L482G1 has been found
in 1968. Last previous edition approved in 2011 as F91 – 06(2011). DOI: 10.1520/ satisfactory.
F0091-06R19. Tygon tubing or equivalent has been found satisfactory for this purpose.
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