This Recommended Practice (RP), IEST-RP-CC001.7, covers basic provisions for HEPA (high efficiency particle arrestance) and ULPA (ultra-low penetration air) filter units as a basis for agreement between customers and suppliers.

HEPA filters and ULPA filters that meet the requirements of this RP are suitable for use in clean air devices and cleanrooms that fall within the scope of ISO 14644 and for use in supply air and contaminated exhaust systems that require extremely high filter efficiency (99.97% or higher) for submicrometer (μm) particles.

This RP describes 11 levels of filter performance and six grades of filter construction. The customer’s purchase order should specify the level of performance and grade of construction required. The customer should also specify the filter efficiency required if it is not covered by the performance levels specified in this RP.

RP 001.7 What is New and Improved:

What is new
• An Appendix with a draft of an alternate filter classification scheme relating classes to filter efficiency consistently instead of the nonsequential letter Types. This being a new proposed scheme, it is included in an appendix for user comments and suggestion and may be considered as a recommended filter class in a future revision.
• An Appendix providing guidelines for system qualification for testing filter sizes with high aspect ratio, i.e., narrow and long. This is based on work done at NASA to test the filters used on the International Space Station.
• Appendix describing operation and results of a low output ‘thermal’ aerosol generator for testing filters. Based on feedback from users, this may be included as a recommended generator in future revisions of the RP.

What is improved
• Text on the testing of filters made with ePTFE or charged media.
• Table D2 edited for improved clarity.
• Cautionary notes on the use of solid aerosol challenge and charge on it.
• Correction of a legacy error in HEPA acronym to High Efficiency Particle Arrestance.

 Supersedes previous versions.

HEPA and ULPA Filters was prepared by Working Group 001 of the IEST Contamination Control Division (WG-CC001).