No More Concerns Over Fine Dust!Building a Safe and Quiet Indoor Environment for Classrooms

- Development of a centralized heating, cooling, air purification, and ventilation system that addresses the indoor noise in classrooms
- Implementation of the world's first plant-soil air purification system and indoor airflow control technology at Sudeok Elementary School

The Korea Institute of Civil Engineering and Building Technology (KICT) has developed a maintenance system that ensures students can enjoy a safe and tranquil classroom environment, free from fine dust. The developed system can supply safe and clean air to classrooms while ensuring that the noise from the Air Handling Unit (AHU) remains below 40 dB at all times.

In 2013, the World Health Organization (WHO) classified fine dust as a Class 1 carcinogen. Fine dust can trigger inflammatory responses in students' bodies, leading to conditions such as asthma, respiratory issues, and cardiovascular diseases. According to the Korea Disease Control and Prevention Agency (KDCA), an increase by 10 μg/m³ in the concentration of ultrafine dust particles (PM2.5) corresponds to a 9% increase in lung cancer incidence. In response, the Korean Ministry of Education announced measures to combat high levels of fine dust in schools in April 2018. It established standards for ultrafine dust (dust particles with a diameter of 2.5 μm or less; a 24-hour average of 35 μg/m³ or less) and installed air purification systems in all schools nationwide by 2021. For active students, it is essential to reduce the concentration of ultrafine dust as much as possible. The WHO has recommended even stricter guidelines, setting the recommended 24-hour average at 15 μg/m³ in 2021.

Typical classrooms in Korea are equipped with separate HVAC systems, each including an air purification system for reducing fine dust. The research team at KICT's Department of Environmental Research has developed a high-performance Air Handling Unit (AHU) and airflow control system capable of performing all functions of air purification, heating, cooling, and ventilation. The developed AHU includes antimicrobial and antiviral filters coated with zinc oxide, ensuring the supply of sterilized and safe air to classrooms. Furthermore, the developed airflow control system optimally positions ventilation diffusers (exhaust ports) to ensure an even distribution of clean air supplied to the classroom indoors.

The setup also includes a plant-soil purification system that continuously reduces indoor fine dust levels while consuming low energy. The plant-soil purification system utilizes both the leaves of plants and the soil itself as filters to remove fine dust particles. Notably, the method of passing indoor air through the soil layer to highly effectively capture fine dust marks a world-first attempt. Using the soil layer as an air purification filter demonstrates an outstanding fine dust purification effect of approximately 40%. During dry winter seasons, the moisture retention capacity of the soil maintains comfortable indoor humidity levels. The application of plant-soil purification filters to a centralized heating, ventilation, and air conditioning (HVAC) system in a school is a world first. The KICT research team constructed a testbed for the actual school environment, including two classrooms and a corridor, to evaluate the performance of the developed technology over approximately two years. They measured the reduction in fine dust levels after implementing the AHU and airflow control system. With the traditional method of placing ventilation diffusers on classroom ceilings, it took 20 minutes to improve fine dust concentrations. However, through research aimed at improving airflow, the team relocated the ventilation diffusers to the side floors of classroom corridors, resulting in a transition from poor fine dust conditions (65 μg/m³) to good conditions (15 μg/m³) in just 13 minutes.

In typical classrooms, air purifiers and other devices often generate noise levels exceeding an average of 55 dB. The KICT research team developed noise reduction technology to maintain a quiet learning environment and succeeded in limiting indoor noise levels to 40 dB or lower. Subsequently, the prototype products validated through the testbed were implemented in two (2) classrooms at Sudeok Elementary School in Yesan, Chungnam Province. This centralized supply system can also be deployed in various other facilities, including multipurpose facilities and offices equipped with air purifiers. The achievements of this development have been published in international journals, such as Atmospheric Environment (2022) and the International Journal of Environmental Research and Public Health (2022). Moreover, this research is being conducted with the support of the National Research and Development Project of the Ministry of Science and ICT and the Ministry of Education from 2019 to 2024.