Where high efficiency filters are fitted, it is important to ensure that the filter and its housing and sealing device do not permit the ingress of particles into a cleanroom or clean zone. This is checked by challenging the filter with an aerosol of particles dispersed upstream of the filter and scanning over the downstream face, frame and gasket of the filter to ensure that there are no leaks that exceed a specified level of penetration.
The object of the in situ leak test described in PD 6609 is to determine if the filter has been damaged between manufacture and installation, and during subsequent use.
In situ testing with oil aerosols might not be acceptable for some cleanroom applications where airborne chemical contamination needs to be controlled, as oil deposited on the filter will outgas.
In such cases, an alternative method that uses inert particles and a particle counter can be used. This method is not discussed in PD 6609 but is described in BS EN ISO 14644-3:2005.
PD 6609 is a Published Document (PD) that provides information supplementary to the provisions of BS EN ISO 14644-3:2005. In particular, it gives recommendations and explanatory guidance for in situ leak testing of high-efficiency filters using an oil aerosol challenge and photometer. It also provides guidance on the procurement of replacement filters, and information that might be required in a test report.
The guidance contained in PD 6609 document is for the leak testing of high-efficiency air filters that can be face scanned. The document does not provide information on other tests carried out on high-efficiency filters installed in cleanrooms, such as pressure differentials, air supply volumes, and airflow uniformity.
Contents of PD 6609 includes:
• Introduction
• Scope
• Normative references
• Requirements for testing
• High efficiency filter specification table
• In situ leak test report
• Bibliography
• Diagram of an aerosol challenge to multiple filters via an air handling unit
• Diagram of aerosol filter testing
• Filter dimensions
• High efficiency filter specification
• In situ leak test report sheet
PD 6609:2007 replaces PD 6609:2000, which has been withdrawn.
