When it comes to industries such as pharmaceuticals, biotechnology, aerospace, semiconductors, and microelectronics, few facilities are as vital as cleanrooms. While many people casually use the term “controlled environment” to describe these spaces, not all controlled environments are true cleanrooms. According to ISO 14644-1, cleanrooms are rigorously defined and classified spaces that follow strict particle concentration limits—making them fundamentally different from standard laboratories or commercial facilities.

In this blog, we’ll explain the official definition of cleanrooms, how they differ from other controlled environments, and why setting a clear design direction early in the project is critical for success.

Cleanroom Definition According to ISO 14644-1

The ISO 14644-1 standard defines a cleanroom as:

A room in which the concentration of airborne particles is controlled and classified, and which is constructed and used in a manner to minimize the introduction, generation, and retention of particles inside the room.

This definition highlights three key aspects:

1. Control: Cleanrooms actively control airborne particles.
2. Classification: They are measured and classified based on particle concentration per cubic meter of air.
3. Construction & Use: Their design, finishes, airflow, and operational protocols are engineered to maintain these conditions.

For example, an ISO Class 5 cleanroom allows only 3,520 particles ≥0.5 μm per cubic meter of air, while an ISO Class 8 cleanroom allows 3,520,000 particles of the same size. This classification system ensures that the required cleanliness level matches the product or process requirements.

Other International Standards for Cleanrooms

While ISO 14644 is the most recognized international standard, several industries and regions also rely on additional guidelines:

• GMP (Good Manufacturing Practice): Used in pharmaceutical and biotech manufacturing, particularly under the EU and FDA frameworks. GMP focuses not only on particle control but also on microbial contamination.
• FS 209E (US Federal Standard, now superseded): Historically used in North America before ISO adoption, but still referenced in older facilities.
• USP <797> and <800>: U.S. standards that specifically cover sterile compounding and hazardous drug handling.
• WHO Annex 2 Guidelines: Global reference for cleanrooms in vaccine and pharmaceutical manufacturing.

Each of these standards complements ISO 14644 but often adds industry-specific requirements for safety, sterility, or regulatory compliance.

Cleanrooms vs. Controlled Environments

It’s important to understand that not every controlled environment is a cleanroom.

• A controlled environment is any space where temperature, humidity, or other environmental factors are monitored and maintained. Examples include data centers, hospital operating rooms, and certain laboratories.
• A cleanroom, on the other hand, is specifically designed and validated to control particulate and microbial contamination, with measurable classification according to ISO 14644-1.

This distinction matters because many decision-makers mistakenly assume that a controlled HVAC system or standard air filtration qualifies a space as a cleanroom—when in fact, the engineering, construction, and certification requirements are far more specialized.

Why Early Design Direction Is Critical in Cleanroom Projects

In commercial, residential, or institutional construction projects, design standards are relatively consistent. Office buildings, schools, and apartment complexes generally follow established codes that don’t vary much from project to project.

Cleanrooms, however, are different. Every cleanroom project must begin with a User Requirement Specification (URS) or Owner’s Project Requirements (OPR) that defines:

• Cleanliness class (ISO Class 5, 7, 8, etc.)
• Temperature and humidity ranges
• Pressure differentials between zones
• Regulatory requirements (FDA, EU GMP, ISO, USP, etc.)
• Material compatibility and process-specific needs

Without this direction established at the earliest project stages, the design and engineering process risks costly scope changes, rework, and even compliance failures. Unlike standard buildings, where systems can be more flexible, cleanroom projects demand precision planning from day one.

Key Takeaways

• ISO 14644-1 defines cleanrooms by particle concentration limits and controlled conditions.
• Other international standards such as GMP, USP, and WHO guidelines add process-specific requirements.
• Cleanrooms are not the same as controlled environments—they are more stringent, regulated, and technically complex.
• Early definition of requirements is critical to avoid costly changes and ensure compliance.

By understanding these differences and aligning on requirements at the start, project owners and design teams can streamline engineering, procurement, and construction, ensuring that cleanroom facilities deliver both compliance and long-term reliability.