Predicting the infection probability distribution due to airborne and droplet transmission

In this study, a method was proposed to predict the infection probability distribution rather than the room-averaged value. The infection probability by airborne transmission was predicted based on the CO2 concentration. The infection probability by droplet transmission was predicted based on occupant position information. Applying the proposed method to an actual office confirmed that it could be used for quantitatively predicting the infection probability by integrating the ventilation efficiency and distance between occupants. The infection probability by airborne transmission was relatively high in a zone where the amount of outdoor air supply was relatively small. The infection probability by droplet transmission varied with the position of the occupants. The ability of the proposed method to analyze the relative effectiveness of countermeasures for airborne transmission and droplet transmission was verified in this study. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Measurement of Ventilation Rate and Evaluation of Infection Risk in a Classroom

To quantitatively evaluate the effect of increasing ventilation using the immediately practicable method on infection risk, the ventilation rate in a classroom was measured by the concentration decay method using CO2. The measured value was then substituted into the Wells-Riley model to evaluate aerosol infection risk in steady and non-steady states. In the classroom, the air change rate per hour (ACH) ranged from 3.1 to 10.2, and the local mean age of air tended to be larger near the outlet. It was also shown that opening the windows increased the ventilation rate the most, resulting in a more evenly distributed local mean age of air. We also showed that the aerosol infection risk in the classroom could be significantly reduced by increasing ventilation, suppressing vocalization, and wearing a mask, compared to some outbreaks of COVID-19. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Effect of Hybrid Workstyles on Productivity of Workers in an Activity-Based Office

This study investigated the effect of hybrid working on the productivity and environmental satisfaction in an activity-based office. Activity-based working is a work style in which workers choose where and when they work. Offices that introduced this concept are known as activity-based offices. To prevent the transmission of COVID-19, hybrid working has become common in Japan after the declaration of the state of emergency. We conducted three surveys in an activity-based office, before, during, and after the state of emergency. The results showed that hybrid working improved workers' perceived productivity. However, the results were influenced by whether the workers valued working with team members at the same location. Workers who valued on-site collaboration saw their productivity decline at home since they found it difficult to communicate. In contrast, others reported higher productivity at home since they found it easier to concentrate, mainly due to the sound environment. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

Variability of Thermal Comfort and Energy Consumption by Introducing Working from Home

Owing to the COVID-19 pandemic, many companies have introduced working from home to avoid the risk of infection. In this study, we conducted questionnaire surveys and analysed the building energy management system (BEMS) in an office building where the number of employees working from home increased after the onset of the pandemic. The influence of working from home on the indoor environment satisfaction and the variability in energy consumption at home and office was determined. The indoor environment satisfaction was significantly higher when working from home than when working at the office. In 2020, the total energy consumption at home and office decreased by 30% in April and increased by 22% in August compared to the previous year. To work from home while saving energy regardless of the season, it is necessary to reduce office energy consumption by decreasing the number of workers present at the office. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.

VENTILATION EFFECT AND THERMAL ENVIRONMENT INDUCED BY ENVIRONMENTAL CONTROL AS A MEASURE FOR COVID-19 IN ELEMENTARY SCHOOL CLASSROOMS WITH MECHANICAL VENTILATION EQUIPMENT IN TOKYO

Air temperature and CO2 concentration were measured in classrooms with ventilation system from April 2018 through March 2022. It is assumed that, under the COVID-19 circumstances, windows of the classrooms, where ventilation system was working, were basically kept open throughout a year. The average air temperature at foot level was 11℃ during winter period because of cold outdoor air infiltration. The estimated ventilation rate tended to decrease during winter period. However, the estimated ventilation rate per person more than 30 m3/h was obtained in case of half number of pupils in the classroom with Hybrid-Flexible lesson for the whole day. © 2023 Architectural Institute of Japan. All rights reserved.

Ventilation Methods against Indoor Aerosol Infection of COVID-19 in Japan

The importance of effective ventilation as one of the measures against COVID-19 is widely recognized worldwide. In Japan, at the early stage of the pandemic, in March 2020, an official announcement was made about basic ventilation measures against COVID-19. WHO also used the term "long-range aerosol or long-range airborne transmission” for the first time in December 2021. Based on the aerosol infection control measures before 2021 by the Japanese government, we conducted experiments on methods related to partition placement as an element of effective ventilation methods. In July 2022, the governmental subcommittee on Novel Coronavirus Disease Control provided an emergent proposal about effective ventilation methods to prevent two types of aerosol infection;infection by large aerosol on the air current and infection by small floating aerosol diffusion in a room. They also showed the way of setting droplet prevention partitions, which do not block off ventilation based on this investigation's results. © 2023 by the authors.