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.

The purpose of this study is to minimize the PCH(Propylene CHlorohydrins) as a by-product in HPMC(HydroxyPropyl MethylCellulose) manufacturing process. HPMC is made of cellulose which is natural high polymer. And HPMC is applicable to several industrial areas. Especially it can be used in food industry as an effective additive. PCH is the by-product which is generated in chemical reaction in HPMC manufacturing process. So it is essential to eliminate PCH for the improvement of product quality. Therefore we have studied to minimize the amount of PCH. It is expected that the application of HPMC could be enlarged as the result of this study.

The purpose of this study is to improve for the inhibition of the generating the PCH(Propylene Chlorohydrins) in HPMC(Hydroxypropylmethyl Cellulose) manufacturing process. HPMC is made of cellulose which is natural high polymer. And HPMC is applicable to several industrial areas. Especially it can be used in food industrial as an effective additive. PCH is the by-product which is generated in chemical reaction in HPMC manufacturing process. So it is essential to eliminate PCH for the improvement of product quality. Therefore we have studied to minimize the amount of PCH. It is expected that the application of HPMC could be enlarged as the result of this study.