AIR QUALITY
Results The quantities of airborne microorganisms for each condition are shown in Figure 2. Through the operating period, the numbers of general bacteria and fungus in fresh air were less than 50 CFU/0.1 m3
and 10 CFU/0.1 m3. In the SH-AC system, the
quantities of both general bacteria and fungus were higher in the humidifier outlet air at the start of the experiment, and decreased thereafter. In the VH-AC system, the quantity of
airborne microorganisms was also higher in the humidifier outlet air at the start of the experiment, and then decreased. Thirteen days after the start of the experiment, the quantity of airborne microorganisms increased slightly. The fluctuation in the quantity of airborne microorganisms at the air conditioner exit during the experiment might be explained by the fact that the accumulated bacteria or fungus were circulated more at the starting period. A slight difference was observed in the quantities of airborne microorganisms in rooms aired by the SH-AC and VH-AC systems. Under both air conditioning systems, the
quantities of general bacteria and fungus in the air of the rooms during the examination were much lower than the regulation level prescribed in the Design and Management Guideline for Hospital Air Conditioners edited by the Healthcare Engineering Association of Japan (HEAS-02-2004). Examination facilities for the air quality
evaluation during a long-term operating period of a vapourisation-type humidification air conditioning system required the air quality of the VH-AC system that was installed in the new Mie University Hospital to be continuously measured after the hospital was opened. In addition, a microorganism suppression device was attached to the other line of the VH-AC system (MCD attached
Figure 2: Schematic flow chart of the test system used in the new Mie University Hospital.
‘There was no difference in air quality from a steam-type humidification air conditioner and a vapourisation-type humidification air conditioner.’
VH-AC system), and compared the quality of air from both the VH-AC and MCD attached VH-AC systems. The suppression control of
microorganisms was conducted by adding a silver ion cassette to the water supply line of the humidification element of the VH-AC system. The Ag ion cassette can produce Ag ions at 0.01-0.03 ppm concentration. In addition, a one-hour dry operation was carried out after a shutdown of the air conditioner. Figure 3 shows the total schematic flow chart of the VH-AC system of the new Mie University Hospital, which was
used in this study. In the VH-AC system of the new hospital, the air supply rate of the air conditioning system was 8,780 CMH, there was 170 CMH of end wind, 66.4 kg/hr of humidification, and the setting conditions were 24˚C, 40%. The air conditioner system was operated from 8:30 to 18:00 except Saturdays, Sundays, and holidays. The sampling was conducted in June,
August, October, November, and December of 2012, and January, February, and March of 2013. General bacteria were cultivated using an SCD agar medium at 36°C for 48 hours, and the fungus was cultivated using PDA+CP
Figure 3: Comparison of the air quality of air-flow from the SH-AC and VH-AC systems. 52 IFHE DIGEST 2015
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