vol.63-6 (2026/3/31)

Utilization of ventilation effectiveness in cleanroom design
(Part 1) Addressing known particle-generation locations

In cleanroom ventilation design, air supply volume flow rate is often determined based on cleanliness class and air changes per hour. However, excessive ventilation rates can lead to increased costs. ISO 14644-4 proposes a formula incorporating ventilation effectiveness (ℰ), which can be obtained via Contaminant Removal Effectiveness (CRE). This study evaluates the applicability of CRE and local air quality index through experiments and Computational Fluid Dynamics (CFD) analysis. Results indicate that using ℰ = 0.5 ensures a largely safe air supply volume flow rate. In CFD analysis, using the 10th percentile local air quality index instead of CRE provides a more conservative estimation of ventilation effectiveness, ensuring a safer design.

Proposal for new cell processing facility design based on simplified entry/exit flow

In cell processing facility (CPF), the risk of cross-contamination between rooms must be minimized while maintaining operational efficiency. This study examines the possibility of omitting doors between rooms by controlling airflow using side walls or push-pull ventilation systems. CFD analysis was conducted to evaluate particle migration characteristics under various conditions. Results showed that both methods achieved particle migration rates below 0.1% without disturbance. Under disturbed conditions, the push-pull ventilation system demonstrated superior performance with approximately 0.8% particle migration compared to 5% with the side wall method.

Study of cleanliness characteristics in vertical and horizontal airflow clean booths

In this study, the particle control performance of vertical and horizontal clean booths, which are designed for work inside, was evaluated by actual measurements and CFD analysis. The analysis was conducted under the same conditions based on the measured data of the cleanliness recovery experiment of the clean booth under the as-constructed condition, and the consistency was confirmed by the material diffusion concentration decreasing with time. Next, the same clean booth was used to measure the ability to control contamination caused by internal particle emission under assumed operational conditions.

Comparison of evaluation result of air filter unit for ventilation according to JIS B 9908 and field test result

Since filter assessment method with artificial dust of JIS B 9908:2019 is different from atmosphere dust trapping in practical use, it is difficult to estimate real lifetime of filter based on test results accordance with JIS test. In this study, a fine filter was evaluated through both the JIS dust loading test and a field test conducted in an industrial area using a one-pass ventilation system. When using a fine filter as a ventilation air filter unit, it is common to install a coarse filter as a pre-filter, so in the field test a coarse filter was installed as a pre-filter. The estimated lifetime derived from the JIS dust fed and measured atmospheric dust concentration was 1,603 hours, whereas the actual lifetime observed in the field reached 8,295 hours, approximately 5.2 times longer. This discrepancy is attributed to differences between artificial and atmospheric dust as well as the load reduction effect of the pre-filter. These findings highlight the limitations of relying solely on JIS test results for lifetime prediction and underscore the importance of evaluation methods grounded in real environmental conditions.

Improvement of toluene wipe cleaning environment by introduction of exhaust auxiliary device

In a work environment where metal fittings are cleaned with toluene, we improvement effect was compared between a single treatment with a hood installed approximately 1 m above the source and a combined treatment with an exhaust auxiliary device. The exhaust volume of the hood was set to be about 1/19 of the theoretical exhaust volume with a control air velocity of 1 m/s near the source, and the air supply volume of the exhaust auxiliary device was set to be about 1/13 of the hood exhaust volume. As a result, the hood alone was in the control class-II, but the combined use of the exhaust auxiliary device improved it to the control class-I. Additionally, it was also effective in reducing the conveying power of the exhaust fan for an upward-suction-type hood.

Cylindrical classifier with Coanda effect

PM_2.5 is having a negative impact on the human health. Filter bag dust collectors, which are widely used in industrial applications, cannot completely prevent PM_2.5 leakage due to their operating principle. Therefore, in order to reduce the amount of leakage from the dust collector to the atmosphere, we investigated by CFD whether it is possible to dust particles of different sizes, including air flows, in a cylindrical classifier using the Coanda effect. The cylindrical classifier is based on the principle of the commonly used cyclone classifier and is equipped with a Coanda Nozzle inside the vessel to prevent the diffusion of small sized dust particles induced inward, creating a Coanda effect. The CFD results showed that about 75% of the classified particles in the size range of 0.1 μm to 2.5 μm and about 67% in the size range of 10 μm to 25 μm were classified. Therefore, it has been demonstrated that the proposed cylindrical classifier possesses sufficient functionality to effectively suppress the leakage of fine particle into the atmosphere.

The certification activities of SIAA
–The spread of antibacterial, antifungal and antiviral processed products–

The Society of International sustaining growth for Antimicrobial Articles (SIAA) was established in 1998 under the corporation of antimicrobial agent manufacturers, antimicrobial product manufacturers, and antimicrobial testing institutions with the aim of promoting proper and reliable antimicrobial products. This paper introduces our activities focusing on the “Antibacterial Processed Product Guidelines” issued by the Ministry of International Trade and Industry (currently known as the Ministry of Economy, Trade and Industry) which indicates the new requirements for the people in the antibacterial industry to take initiative, “What is the SIAA Mark”, “Antibacterial Processed products with SIAA Mark” and “the number of SIAA members”, in addition to our public relations activities to disseminate the SIAA mark in Japan and overseas, and global promotion to establish the SIAA certification system overseas.

Microbiological key points for BCR management and monitoring

BCR, biological cleanroom has been used for Medical, Pharmaceutical company and hospital to protect final product and human etc. from microorganisms. Although its basic structure is similar to that of an ICR (Industrial clean room), the primary differences in their respective purposes and management approaches. This paper provides an overview of the fundamental aspects of BCRs, focusing on key topics including the management.