The Institute of Environmental Sciences and Technology (IEST) has published IEST-RP-CC002.5, Unidirectional-Flow, Clean-Air Devices, the first update since 2016 of its widely used Recommended Practice covering the definitions, evaluation procedures, and major requirements for unidirectional-flow, clean-air devices.

Developed by IEST Working Group 002, a standards body made up of manufacturing professionals and end users, this edition supersedes IEST-RP-CC002.4 (2016) and reflects years of technical review aimed at improving clarity, testing consistency, and real-world applicability for both manufacturers and field-certification professionals.

IEST-RP-CC002 serves as a foundational reference for the specification, procurement, and certification testing of unidirectional-flow clean-air devices with self-contained motor blowers and powered terminal units with replaceable filters, and provides guidance for customer-directed recertification of existing equipment.

“This newest release of IEST-RP-CC002.5 builds on a foundation of supporting the certification of clean-air device testing with updated test methods and requirements,” said Mark Hallworth of Particle Measuring Systems, and the IEST Contamination Control Technical Vice President. “The importance of defining the acceptance criteria and how to test, ensuring those requirements are met, gives assurances that the device is suitable for use and meets the expectations for operation. Without measurement, there is no control; and this document defines those measurements.”

What’s New in This Edition
Test tiers have been reframed: primary- and secondary-level testing is no longer split into mandatory versus optional, but instead tied to what regulatory standards, manufacturer specs, or customer requirements actually call for.

• Airflow velocity testing (6.1.1) has been streamlined, dropping to one reading per sampling location with a revised tolerance criterion.
• The induction leak and backstreaming sections (6.1.3–6.1.4) are now two distinct tests with their own acceptance criteria. Backstreaming is qualitative and visual-medium only, while induction leak testing shifts to an aerosol photometer method or a discrete-particle counter method (failure on a continual-increase trend), replacing the old 1×10⁻³ ambient concentration threshold.
• Brand-new Section 6.3 covers site installation assessments, microbial environmental monitoring (referencing USP <1116> and CETA CAG-009), and the relocation of filter differential pressure testing into that new tier.
• Also new: a widened vibration frequency range; a raised ULPA filter efficiency minimum; and a new Section 6.1.6 on airflow visualization studies referencing CETA CAG-014.

These updates are designed to give manufacturers and field-certification professionals clearer, more consistent criteria for verifying that unidirectional-flow clean-air devices perform as intended. The full scope of changes — including specific test procedures, thresholds, and new appendices — is detailed in the published document.

Whether you’re running field certifications or manufacturer testing, these changes will touch your protocols directly — grab your copy of IEST-RP-CC002.5 from the IEST Bookstore and get ahead of the update before your next certification cycle.