Examination of the Optimal Environment of Unilateral Laminar-Flow Clean Benches for Sterile Preparation Based on Wind Velocity Measurements

Abstract

A clean bench is necessary for maintaining an environment compliant with Class 5 of the International Organization for Standardization 14644-1 (ISO Class 5), ensuring airflow through the workspace with a mean wind velocity of 0.3-0.6 m/s as delineated by Japanese Industrial Standards (JIS) B9922. This study emphasizes wind velocity as a crucial factor influencing ventilation rates and measures wind velocity across various vertical and horizontal planes with respect to the work surface in three different models of clean benches. The findings indicate that among the models tested, the median wind velocity within 15-30 cm from the sash met JIS standards. However, the median wind velocity showed wide variation on the planes at 0-20 cm height from the work surface, while the variation was narrow on planes covered by the sash at 20-50 cm height from the work surface, yielding a constant wind velocity. These observations led to the identification of the optimal preparation area across the models as being "at least 20 cm above the work surface and within a 15-30 cm depth from the sash, with the sash opening maintained at or below 20 cm. This designated area minimizes the risk of particulate and microbial contamination of the prepared drug products, offering a standardized guideline for clean bench operation to ensure product and environmental safety.