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AIR QUALITY Norihiro Nishimura – Vice President, Mie University


Steam and vapourisation: humidification compared


This study compares the performance of a steam-type humidification air conditioning system (SH-AC system) and a vapourisation-type humidification air conditioning system (VH-AC system) at Mie University Hospital in Japan.


The Mie University Hospital facilities were used to compare the control of a microbe component of air flow. The facility has two buildings – the old hospital, which was built more than 40 years ago, and the new hospital, which was opened in January 2012. We installed a steam-type humidification


air conditioner and a vapourisation-type humidification air conditioner in the old


hospital, and evaluated the quality of air flow from each air conditioner. There was no difference in air quality between steam and vapourisation-type humidification. A VH-AC system was installed in the new


hospital in 2012, and the air quality was continuously measured for one year. We confirmed that adding silver ions was effective for stabilising the air quality in the long-term operation of the vapourisation- type humidification air conditioner. A comparison of the air quality of airflow


from the SH-AC system and the VH-AC system saw the steam-type humidifier being installed in the air conditioning system of the east ward of the old Mie University Hospital, the demolition of which has been planned. We


installed a vapourisation-type humidifier as a bypass line into the steam-type humidification air conditioner of the hospital, to evaluate the air quality of each system. Figure 1 shows a total schematic flow chart of the test system used in this study. The humidification air conditioning system provided the air conditioning of the first to third floors, and was operated from 8:30 to 18:00 except Saturdays, Sundays, and holidays. In this study, the air supply rate of the air conditioning system was 5,000 CMH (cubic meters per hour), and the quantity of humidification was 30 kg/hr.


Method of measurement Each air conditioning system was operated for two weeks at a time, and the airborne microorganisms were collected using an air sampler. General bacteria were cultivated using Soybean-Casein Digest Agar Medium (SCD agar medium) at 36˚C for 48 hours, and the fungus was cultivated using Potato Dextrose Agar with Chloramphenicol medium (PDA+CP medium) at 26˚C for 48 hours. The quantity of microorganisms was measured as the number of colonies after cultivation, and the mean of three plates is shown in the results. The sampling points of airborne microorganisms were outside the air inlet, humidifier inlet, humidifier outlet, and inside the room. The sampling was conducted on the first day, and six and 13 days from the start of the study.


Norihiro Nishimura


Norihiro Nishimura graduated from Tsukuba University with a BA in Biochemical engineering in 1987. He went on to gain a PhD in Molecular Biology at Tsukuba University in 1995.


He began employment at Mie University in 2004 as a Management Professor at Medical/Industrial Linkage Office, Mie University School of Medicine. In 2010 he became Director at Community-University Research Cooperation Office, Community-University Research Cooperation Center, Mie University, and Assistant to the President, Mie University in 2011; Director at Creative Research & Development Institute, Mie University in 2011; and Director at Regional Area Strategy Center, Mie University and; Vice President, Mie University in 2013.


Figure 1: Schematic flow chart of test systems used in the old Mie University IFHE DIGEST 2015 51


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