Designing for ISO Class Cleanrooms: HVAC, Pressure, and Particle Control

As semiconductor, pharmaceutical, and battery manufacturers push the limits of precision, the demand for ISO-classified cleanrooms has never been higher. Designing these spaces goes far beyond installing HEPA filters. It requires a comprehensive understanding of airflow engineering, pressure zoning, and contamination control strategies. We will explore the critical design elements needed to meet ISO cleanroom classifications, with a focus on HVAC systems, pressure differentials, and particle control.

HVAC Design: The Heart of Cleanroom Control

HVAC is the backbone of any cleanroom environment, as it governs both air cleanliness and thermal conditions

Air Change Rates

• ISO 5 rooms may require 240-480 air changes per hour (ACH).

• ISO 7 spaces can operate with 30-60 ACH.

• These high rates are achieved with powerful Fan Filter Units (FFUs) or centralized air handlers.

Filtration

• HEPA (99.97% @ 0.3µm) or ULPA (99.9995%) filters are standard depending on ISO class.

• Filters are often located at ceiling diffusers or within FFUs for modularity.

 Temperature and Humidity

• Semiconductor fabs: 20-23°C with ±1°C tolerance and 40-55% relative humidity.

• Battery dry rooms: Can require <1% relative humidity with dew points below -40°C.

Pressure Cascades: Zoning for Containment

Maintaining positive or negative pressure differentials is essential to control particle migration between spaces.

Common pressure zoning:

• ISO 5 Process Area: +15 Pa (relative to ISO 6)

• Gowning Room: +5 to +10 Pa (buffer between ISO 7 corridors and ISO 5 workspace)

• Airlocks: Designed with interlocking doors to prevent pressure loss

A well-designed cascade ensures particles always flow away from critical zones, never towards them.

Particle Control: More Than Just Air Filters

Material Selection

• Use non-shedding, easy to clean finishes like stainless steel, epoxy coatings, and vinyl floors.

Cleanroom Behavior Protocols

• Enforce strict smocking rules, limit entry points, and install sticky mats and air showers.

Room Layout

• Keep laminar flow zones obstruction-free.

• Separate “clean” and “dirty” corridors for material and personnel flow.

Monitoring Systems

• Install real-time particle counters in ISO 5 zones and maintain calibration logs.

Designing Cleanrooms the BBTech Way

At BBTech America, our cleanroom designs are integrated from concept stage through installation and commissioning, using digital simulation and modular construction to reduce field errors. We understand the importance of:

• Integration HVAC with process utility piping

• Designing for flexibility and future upgrades

• Meeting strict ISO standards without compromising energy efficiency

Designing for ISO Class cleanrooms is a high-stakes process requiring coordination between mechanical, electrical, architectural, and process teams. HVAC systems must deliver high-volume, clean air; pressure zoning must be meticulously controlled; and every material and protocol must serve the goal of particle minimization.