Hospital Cleanroom Standards: ISO 5–8 Guide for Operating Theaters
In modern healthcare infrastructure, air quality is a clinical control parameter—not just an engineering metric. At ICARELIFE, we specialize in modular operating theaters where airborne contamination control is the foundation of patient safety.
This definitive guide explains how ISO 5, 6, 7, and 8 cleanliness classes are applied in hospital projects, how they align with global standards, and how to select the right specification without over-designing.
What ISO 14644-1 Means in a Hospital Context
ISO 14644-1 defines cleanliness based on particle concentration per cubic meter. While industrial cleanrooms use these as absolute targets, hospitals apply them based on Surgical Risk Levels.
| ISO Class | Max Particles (≥0.5µm) | Clinical Application | Airflow Concept |
|---|---|---|---|
| ISO 5 | 3,520 | Local Sterile Field (Surgical Table) | Unidirectional (Laminar) |
| ISO 6 | 35,200 | Specialized Labs / Technical Suites | Mixed / Controlled |
| ISO 7 | 352,000 | Operating Theater Background | Mixed / Turbulent |
| ISO 8 | 3,520,000 | Scrub Rooms & Clean Corridors | Turbulent / Dilution |
Global Standards Alignment
Whether you follow ASHRAE (USA), HTM (UK), or GB (China), the underlying physics of cleanroom performance maps directly back to ISO levels.
| Region | Standard | Room Background | Sterile Field |
|---|---|---|---|
| United States | ASHRAE / FGI | ISO 7 | ISO 5 |
| United Kingdom | HTM 03-01 | ≈ ISO 7 | Ultra-Clean (≈ ISO 5) |
| China | GB 50333 | Class 10,000 | Class 100 |
Engineering Authority: Air Changes & Flow Patterns
Achieving ISO 5 for the surgical field requires Laminar Airflow (LAF). This creates a piston-like effect, pushing contaminants away from the incision site.
| Area | Typical ACH | Primary Goal |
|---|---|---|
| Surgical Field (ISO 5) | 240–300 (Local) | Infection Prevention at Site |
| Full OR (ISO 7) | 20–25 | Particle Dilution |
| Anterooms (ISO 8) | 15–20 | Pressure Cascade Maintenance |
Why ISO 6 is Rare in Operating Theaters
ISO 6 is technically a "middle ground." It is cleaner than a standard background (ISO 7) but does not provide the absolute protection of a laminar zone (ISO 5). In practice, most hospitals choose the efficiency of ISO 7 and the local protection of ISO 5 to minimize energy consumption while maximizing clinical safety.
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