ISO Clean-Room
ACH Auditor
Audit volumetric air changes per hour (ACH) and design supply airflow parameters to guarantee international clean-room compliance criteria.
ISO 14644-1 Airflow Mechanics & Volumetric Dilution Calculus
Unlike commercial building ventilation profiles designed solely for thermal comfort, clean-room ventilation is calculated as an explicit particulate dilution protocol governed by international ISO 14644-1 standards. Airborne particle displacement relies entirely on high Air Changes Per Hour (ACH). As clean-rooms transition from ISO Class 8 (up to 3,520,000 particles ≥0.5 μm per m³) down to ISO Class 5 (maximum 3,520 particles ≥0.5 μm per m³), the required mechanical design transitions from turbulent, non-unidirectional airflow patterns to strict, continuous laminar downward streams. The mathematical relationship dictates that ACH is directly proportional to cumulative Fan Filter Unit (FFU) supply volume and inversely proportional to the raw envelope cubic volume. Underloading the air exchange rate allows particulate concentrations to settle out onto clean work surfaces, instantly breaching process cleanliness criteria.
Frequently Asked Questions
A: While over-ventilating guarantees excellent particulate numbers, it creates a massive energy burden. Fan power requirements scale cubically with airflow speed according to fan laws. Operating an ISO Class 7 zone at 150 ACH instead of its optimized 45 ACH needlessly spikes central plant operating costs and can generate excessive turbulent eddies that trap particles near structural partitions.
A: Clean-room states are evaluated across three distinct parameters: As-Built, At-Rest, and Operational. Human operators are the primary source of particulate sheds inside clean-rooms. A room operating with high machinery automation can maintain its ISO class target with a low ACH profile, whereas a room packed with dense manual labor shifts requires a configuration pushed to the peak of its targeted ACH range to continuously sweep away human shedding.