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INFECTION CONTROL


Average 9.22 W/m2


Fungi 570 Elevation plan


Evaporative humidifier


65


14-15 13-14 12-13 11-12 10-11 9-10 8-9 7-8 6-7 5-6 4-5 3-4 2-3 1-2 0-1


Floor plan


(UV intensity measured at 40 mm distance from the humidifier/drain pan).


Figure 6: Layout of UV light lamp and measured UV intensity.


‘The impact of the difference in measures for the pollution control of evaporative humidifiers is low.’


found to be cleaner in all humidifiers. Comparing the measurements for pollution control, no superiority was observed in cleanliness. In addition, all the humidified air results met the standards. As shown in Figure 8(A), the degree of


contamination on the inside wall surface of the AHUs was exceptionally low, and no procedure related to time was performed. In Case C, the surface was highly clean due to the ingress of light from the UV light lamp for the humidifier to the CAV chamber. Few fungi were detected in the humidifier elements as shown in Figure 8(B). In Case C, the number of microorganisms on the humidifier element increased significantly as time advanced. The


74


200 180 160 140 120 100 80 60 40 20 0


Fungi


Microorganisms


Humidified air AB C Figure 7: Evaluation of number of airborne microorganisms. A


200 180 160 140 120 100 80 60 40 20 0


Inside wall surface of AHUs 1.E+08


Fungi Microorganisms


1.E+06


Fungi Microorganisms


B Humidifier element D


humidification


Air before


Outdoor air


1.E+04


1.E+02


1.E+00


AB C


D Figure 8: Evaluation of number of attached microorganisms.


exact cause is uncertain, but the high surface temperature due to UV light irradiation might have encouraged the growth of microorganisms. The small number of microorganisms of


the humidifier element in Case D shows the potential advantage of the drying operation against odour and other problems. Figure 9 shows the results of a preliminary study


comparing the number of microorganisms of the humidifier element before and after the drying operation after a long period of humidification. In this experiment, the drying operation had a restraining effect against microorganisms. In the evaluation of the drainage water, no Legionella species was detected. After continuous operation for an


IFHE DIGEST 2014


AB C


D


820 580 150 150 220


820


Number of microorganisms [CFU]


December 2 January 25 March 2


December 2 January 25 March 2


December 2 January 25 March 2


December 2 January 25 March 2


Number of microorganisms [CFU/g (mL)]


December 2 January 25 March 2


December 2 January 25 March 2


December 2 January 25 March 2


December 2 January 25 March 2


December 2 January 25 March 2


December 2 January 25 March 2


December 2 January 25 March 2


December 2 January 25 March 2


December 2 January 25 March 2


December 2 January 25 March 2


Number of microorganisms [CFU]


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