ISO 14644-17:2021

Overview

ISO 14644-17:2021 - "Cleanrooms and associated controlled environments - Part 17: Particle deposition rate applications" provides guidance on interpreting and applying measurements of particle deposition rate (PDR) and particle obscuration rate on vulnerable surfaces in cleanrooms. The standard focuses primarily on macroparticles (notably particles >5 µm) in the operational state and shows how PDR measurements can be used within a contamination control programme and a risk assessment process to protect product- and process-critical surfaces.

Key topics and technical requirements

• Scope and purpose: Defines how to use PDR data to set limits for macroparticles on vulnerable surfaces and to assess contamination risk. It clarifies what is not covered (it does not provide a classification scheme for PDR/obscuration rates, does not specifically treat microbiological carriers, and excludes contact-transfer deposition).
• Measurement methodology: Describes methods to measure particle deposition rate on surfaces (see Annex A/B) and alternatives such as the particle obscuration rate (Annex C) for light-sensitive optics and similar applications.
• PDR definition and basic formulas: PDR is the change in surface particle concentration per area per hour and can be used to estimate deposited particle counts:
  • PDR (number·m⁻²·h⁻¹) = (C_f − C_i) / (t_f − t_i)
  • Estimated number deposited: N = PDR × area × exposure time
• Interpretation and risk assessment: Guidance on deriving acceptable PDR limits from product-critical contamination thresholds and on assessing whether PDR measurements demonstrate control.
• Factors influencing deposition: Emphasizes mechanisms such as gravity, air turbulence and electrostatic attraction and the role of personnel and equipment activities. Notes that particles >10 µm are largely removed from air by deposition (>50%), and >40 µm deposit even more (>90%).
• Documentation and monitoring: Requirements for recording PDR results, correlating PDR peaks with activities, and using results to adjust procedures or controls.

Practical applications and users

ISO 14644-17 is applicable to industries where surface contamination by macroparticles matters:

• Pharmaceuticals, medical devices, and healthcare manufacturing
• Microelectronics and semiconductor fabrication
• Optics, aerospace, and precision assembly (mirrors, lenses, solar panels)
• Nuclear, food, and other contamination-sensitive production Typical users: cleanroom engineers, quality and contamination control managers, process engineers, validation teams, and facilities operations staff who need to define surface contamination limits, monitor deposition, and reduce contamination risk.

Related standards

• ISO 14644-1 (cleanroom classification by airborne particles)
• ISO 14644-3 (test methods)
• ISO 14644-9 (surface particle concentration)
• IEST-STD-CC1246E (surface cleanliness specifications)

Keywords: ISO 14644-17, particle deposition rate, particle obscuration rate, cleanrooms, contamination control, vulnerable surfaces, PDR measurement, cleanroom monitoring, risk assessment.