Why ISO Classification Matters

Every cleanroom and controlled environment project start with the same question: “What ISO Class do we need?”

The answer matters because ISO Classification sets the standard for how clean your environment must be. Based on ISO 14644-1, this system limits the number of airborne particles allowed per cubic meter. In industries like pharmaceuticals, biotech, semiconductors, and advanced manufacturing, the right classification ensures compliance, protects product quality, and reduces costly risks.

However, the numbers can feel confusing. Why does ISO Class 5 carry more weight than ISO Class 8? How do filters and HVAC design impact performance? And what role do modular cleanrooms play in meeting compliance quickly?

Let’s break it down.

What ISO Classes Actually Mean

An ISO Class is essentially a cleanliness scorecard. The smaller the number, the fewer particles permitted in the space.

For example:

• ISO Class 8 resembles a standard office environment, where thousands of particles float in the air.
• ISO Class 5 is closer to an operating room, with far stricter limits.

Therefore, the right classification ensures that the space aligns with industry needs and regulatory requirements.

How Cleanrooms Achieve the Right ISO Class

Filtration with HEPA and ULPA Filters

Filters do the heavy lifting in cleanrooms.

• HEPA filters capture 99.97% of particles ≥0.3 µm.
• ULPA filters go even further, trapping particles down to 0.12 µm.

As a result, proper filter selection plays a direct role in meeting the target, ISO Class.

Air Changes Per Hour (ACH) and HVAC Design

The volume of clean air introduced into a space each hour—known as air changes per hour—determines how quickly contaminants get removed.

• ISO Class 8 may require about 20 ACH.
• ISO Class 5 often needs 240–400 ACH.

In short, HVAC design directly affects compliance, energy efficiency, and operating costs.

Pressurization and Smart Layouts

Positive pressure keeps dirty air out of clean areas. In addition, smart layouts with airlocks, material flow corridors, and controlled personnel movement reinforce compliance.

Modular Cleanrooms: Flexible and Scalable

More companies now choose modular cleanrooms because they deliver:

• Faster installation.
• Easy scalability as operations expand.
• Pre-engineered solutions that simplify ISO Class compliance through ease of cleanability

Moreover, modular systems reduce downtime compared to traditional construction.

ISO Classes in Different Industries

The correct ISO Class varies by industry, but the principle remains the same: fewer particles = higher protection.

• Pharmaceuticals and Biotech: ISO Class 5–7 safeguards sterile production.
• Semiconductors and Electronics: ISO Class 4–6 prevents microscopic defects.
• Medical Devices: ISO Class 7–8 balances compliance with cost efficiency.

In addition, choosing the correct ISO Class ensures alignment with GMP, FDA, and EU GMP Annex 1 standards.

Key Takeaway

ISO Classifications are not mysterious codes. Instead, they serve as a roadmap for compliance and safety in cleanrooms, controlled environments, and modular facilities. By selecting the correct class, companies protect their products, ensure regulatory approval, and optimize long-term operations.

At Cleanroom Catalyst, we specialize in turning ISO 14644-1, ASHRAE guidelines and other related codes / standards into practical, cost-effective cleanroom designs.

Contact us today to explore how the right ISO Class can support your next project.