There are very few reports concerning with the environmental hygienic survey on the long term utilized clean room. Then in this time, fallen bacteria and fallen fungous count, floating bacteria, floating dust count, temperature, humidity, CO
2 concentration, precipitated bacterial count and bacteria in water were studied in comparison between the horizontal air flow system and the vertical air flow one which were used for the leukemic patients. Though it is known that the cleanliness of a clean room maintains the class 100 on NASA standard, the cleanliness in the clean room, wl studied, after the long term utilization is much lower than the class 100.
In the horizontal air flow system, many bacteria and fungi could be detected especially at the floor both under the bed and the water space.
In the vertical system, the similar results could be obtained, although the degree of cleanliness was lower than that in the horizontal one.
The followings might cause the contamination;
1) incorrect laminar air flow, 2) bacteria which were from patient's goods (including a bed), water, water space and floor, 3) bacteria which were carried to the bioclean room from outside.
It is difficult to detect the contamination by the determination of fallen bacteria and of floating dust count alone, therefore, it may be considered that the determination of precipitated bacteria and bacterial count in water should be checked.
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