A study was conducted to evaluate the proper particle cleaned air changes per hour (PCH) in apartment buildings and school classrooms. The concept of PCH was newly introduced. The PCH can be expressed as the clean air delivery rate (CADR) per space volume. The PCH includes the filtering effect with air changes per hour (ACH). A method for calculating the proper PCH was theoretically proposed and experimentally verified. The proper PCH to effectively control ultrafine particles in apartments and school classrooms was found to be 4.0/h and 4.2/h, respectively. In general, air cleaners and mechanical ventilation devices are often used together in apartments and school classrooms. In such cases, it is important to consider the proper PCH of each device and control it for energy-efficient operation. In addition, in times of concern for infection such as COVID-19, it will be necessary to operate the PCH at 6.0/h or more to minimize the probability of infection.

Abstract
1. 서 론
2. 연구 방법
    2.1 공기청정횟수와 입자청정횟수
    2.2 적정 공기청정횟수 산정
    2.3 실험 방법
3. 결 과
    3.1 공동주택 적정 입자청정횟수
    3.2 학교 교실 적정 입자청정횟수
4. 고 찰
5. 결 론
References

• 우수창(LG전자 에어케어사업담당) | Suchang Woo (Air Care Business Division, LG Electronics Inc.)
• 노광철(에어랩(주)) | Kwangchul Noh (Air Lab Inc.) Corresponding author