vol.63-2 (2025/7/31)

Improvements and issues in indoor air quality through ventilation

The purpose of ventilation is to provide clean air to occupants in the building. Therefore, ventilation is generally defined as “the introduction of unpolluted outdoor air into a room and the removal and dilution of polluted indoor air to the outside”, thereby ensuring a healthy and comfortable environment in the occupied areas. In this paper, an overview of the ventilation rate required for indoor air quality, and the concept of ventilation efficiency and various ventilation efficiency indices are introduced. The evaluation results of the effective ventilation with air purifiers using the Wells-Riley model, which predicts the probability of infections.

Trends in performance evaluation test methods for household air cleaners

Household air cleaners have attracted attention for air pollution control by PM_2.5 and hay fever control. However, due to the recent pandemic of the novel coronavirus (COVID-19), the effect of air cleaners on virus removal and control is attracting worldwide attention. On the other hand, there are many performance evaluation test methods (JEM 1467 (Japan), GB/T 18801 (China), AHAM (USA), etc.) unique to each country, so it is urgent to establish an international standard test method. Our country has developed an evaluation test method for determining the removal performance of air cleaners against airborne viruses by Japan Electrical Manufacturers’ Association (JEMA) : JEM1467 Annex D “Evaluation test of air purifier removal performance against airborne viruses”, ahead of the rest of the world, and has used it to display the performance of air cleaners. However, since it is positioned as a voluntary standard in the domestic home appliance industry, it is necessary to establish an international standard for airborne virus removal performance evaluation test method.
This paper describes the trends in performance evaluation test methods for household air cleaners, the activity status of IEC/TC59/SC59N, and the international standard (IEC 63086-1, IEC 63086-2-1, IEC 63086-2-2, IEC 63086-2-3) on performance evaluation test methods.

Pollutant removal performance of room air cleaners using with test methods of IEC63086 and revised JEM1467

This paper describes the actual contaminant removal performance of room air cleaners using with the latest test methods of IEC 63086 or the revised JEM1467.
As results by our tests, the following findings have been obtained.
1) The CADR for particulate matter including allergenic particles such as pollen, mites, pets are larger than that for gaseous one.
2) For particulate collection including ultrafine particle and fungi, their CADR are proportional to the size of the equipment air flow.
3) Gaseous substances such as toluene, acetaldehyde and formaldehyde have smaller CADR than particulate matter one. Especially acetaldehyde is a difficult substance to remove.

Indoor air quality improvement in smoking room using tobacco deodorizer
A case study of an energy-saving smoking room installed in an office building

The design of ventilation systems for smoking rooms must prevent the leakage of tobacco smoke and reduce harmful substances within the room. However, it often requires large airflow volumes to adequately decrease particulate matter and odors. To overcome these challenges, we developed a smoking room system that balances improved air quality with energy efficiency. This system incorporates tobacco deodorization devices, displacement ventilation, and variable air volume control based on occupancy detection. We validated the system in an actual office building, and the following results were obtained: (1) We achieved an effective smoke isolation with no leakage from the smoking room. (2) The concentrations of suspended particulates and carbon monoxide were kept low. (3) The system was estimated to reduce annual primary energy consumption by approximately 60% compared to conventional constant air volume systems. (4) User surveys indicated a noticeable reduction in odor perception. By installing such deodorizing equipment and an optimized ventilation control system, this approach enables achieving both a comfortable indoor environment and improved energy efficiency.

Improvement of perceived air quality by removing human bioeffluents with an air purifier

The use of air cleaners to enhance indoor air quality under reduced ventilation has attracted increasing attention in the context of energy conservation. However, their effectiveness in removing gaseous pollutants, especially human bioeffluents, remains insufficiently understood. This study evaluated the performance of a gas-phase air cleaner equipped with modified activated carbon under conditions where bioeffluents were the dominant source of indoor pollution. Two male participants sat in a stainless-steel chamber at two temperatures (23°C and 28°C), while an air cleaner was either operated or idled. Thirteen additional participants assessed perceived air quality, and chemical analyses were conducted to measure pollutant concentrations. The results demonstrated that human-emitted pollutants were effectively removed even under conditions marked by CO₂ concentrations exceeding 3,000 ppm. Sensory evaluations confirmed reductions in odor intensity and percentage of dissatisfaction. Furthermore, the effectiveness of the air cleaner was more pronounced at 28°C, potentially due to increased emission rates and enhanced chemical reactivity at higher temperatures. These findings suggest that gas-phase air cleaners can contribute to maintaining air quality in poorly ventilated spaces where human emissions dominate. Continued knowledge accumulation, including field validation, is needed to develop robust evaluation methods that accurately assess air cleaner effectiveness.

Predicting effect of installing an air cleaner based on material balance

When an air cleaner is applied to a room with ventilated facilities to improve its indoor air quality, predicting the effect of selected air cleaner prior to installation is desired. This paper presents a diagram that roughly predicts the effect of installing an air cleaner at different ventilation rates based on the relationship between its single-pass efficiency and the rate of indoor air passage through it using a simple model that assumes instantaneous uniform diffusion of the contaminants of interest. In the results, the diagram was found to readily provide information about the required performance of air cleaners such as the clean air delivery rate (CADR) and equivalent air change rate at the planning stage.

Contamination control and air cleanliness classification in clean rooms

This paper focuses on the classification of air cleanliness and the associated testing methods based on the Japanese Industrial Standard JIS B 9920-1. It provides detailed information on precautions when using an LSAPC (Light Scattering Airborne Particle Counter) for sampling, as well as selection criteria based on the performance and functionality. The aim is to provide practical knowledge that enables practitioners to carry out efficient, reliable, and standard-compliant cleanroom classification.