The Difference Between ISO 4 And ISO 5 Cleanrooms

Comprehensive Guide to CleanRoom Classifications, Standards, and Applications

In high-tech industries like microelectronics, pharmaceuticals, and biotechnology, cleanrooms are critical for ensuring product quality and controlled manufacturing environments. The ISO 14644-1 standard classifies cleanrooms based on the number of airborne particles per cubic meter, with ISO 4 (Class 4) and ISO 5 (Class 5) being two widely used high-level classifications.

This article examines the core differences between ISO 4 and ISO 5 Cleanrooms in particle counts, applications, design requirements, operational monitoring, and costs to help you select the appropriate classification for your needs.

Core Difference: Particle Count Limits (iso 14644-1)

The ISO 14644-1 standard defines cleanroom classes based on the maximum allowable particles per cubic meter of air. ISO 4 and ISO 5 cleanrooms have significant differences in particle control:

Particle Size (µm)	ISO 4 (Class 4) Max Particles/m³	ISO 5 (Class 5) Max Particles/m³
≥ 0.1	≤ 10	Not Specified
≥ 0.2	≤ 2	Not Specified
≥ 0.3	≤ 75	≤ 1,020
≥ 0.5	≤ 283	≤ 3,520
≥ 1.0	Not Specified	≤ 832
≥ 5.0	Not Specified	≤ 29

Key Insight: ISO 4 cleanrooms have exponentially stricter requirements for sub-0.5µm particles compared to ISO 5. This difference directly impacts design, construction, and operational costs.

ISO 4 (Class 4) Cleanroom Specifications

Ultra-Clean Environment · Nanoscale Particle Control

Core Characteristics: Focuses on extreme control of 0.1µm and 0.2µm particles for the most sensitive manufacturing environments.

Unidirectional airflow in ISO Class 4 cleanrooms

Typical Applications

Semiconductor lithography
Nanotechnology manufacturing
Advanced sterile fill-finish (biotech/pharma)
Critical R&D laboratories
Micro-electromechanical systems (MEMS) fabrication

Design Requirements

Requires ULPA filtration (≥99.9995% @ 0.12µm) or advanced HEPA
Unidirectional (laminar) airflow over critical zones
Very high air change rates (typically >500 per hour)
Seamless, non-shedding materials
Advanced sealing techniques

ISO 5 (Class 5) Cleanroom Specifications

High-Clean Environment · Micron Particle Control

Core Characteristics: Focuses on ≥0.5µm particle control, balancing cleanliness requirements with cost-effectiveness.

ISO 5 cleanroom with personnel working

Typical Applications

Electronics assembly (HDDs, optics)
Pharmaceutical compounding & filling (non-sterile)
Medical device assembly
Biological safety cabinets
Pharmaceutical packaging

Design Requirements

Uses HEPA filtration (≥99.97% @ 0.3µm)
Primarily non-unidirectional (turbulent) airflow
High air change rates (200-400 per hour)
Robust construction materials
Laminar flow hoods for critical zones

Key Operational Differences

Aspect	ISO 4 (Class 4)	ISO 5 (Class 5)
Operational Monitoring	Continuous/per shift real-time particle monitoring (≥0.1µm) with strict alarms	Regular monitoring (daily/weekly/per batch), real-time for critical zones
Gowning Requirements	Multi-layer (hood, coverall, boots, gloves, facemask/goggles), ultra-low shedding materials, mandatory air showers	Full coverage (coverall, bouffant, beard cover, gloves, boots), low-linting materials, air showers common
Risk Level	Highest: Nanoscale particles cause catastrophic failure	High: Larger particles cause significant defects/failures
Cost Analysis	Very high: Complex design, ULPA filters, intense monitoring, strict gowning	High: Less complex than ISO 4, HEPA filters, frequent monitoring

Cleanroom ISO4 vs ISO5 Cost Comparison Analysis

Relevant ISO Standards

Cleanroom design, construction, and operation follow these key international standards:

ISO 14644-1: Classification by Air Cleanliness (Particle Concentration)
iso 14644-2: Monitoring for Compliance
ISO 14644-4: Design, Construction & Startup
iso 14644-5: Operations
ISO 14698: Biocontamination Control
ISO 9001: Quality Management Systems

ISO standard documents with cleanroom background

How to Choose Between ISO 4 and ISO 5

Key Decision Factors

Process Sensitivity: How tolerant is your process to particle contamination?
Particle Size Requirements: What is the smallest particle size that would cause failure?
Industry Regulations: Does your industry have specific requirements (e.g., cGMP for pharma)?

Selection Recommendations

Choose ISO 4 when: Your processes are extremely sensitive to nanoscale particles (≥0.1µm) where any contamination would cause catastrophic failure (e.g., semiconductor manufacturing, advanced sterile filling).

Choose ISO 5 when: Your primary goal is controlling ≥0.5µm particles and your process has tolerance for sub-micron particles (e.g., electronics assembly, medical device manufacturing).

Consider total lifecycle costs (construction, certification, monitoring, maintenance) and consult with cleanroom design professionals for your specific application.