| 摘要 |
A fan filter unit for use in cleanrooms is provided, which decreases efficiently the concentration of chemical substance existing in the atmosphere while the expansion of the air circulating space and the electric power consumption increase of the fan-driving motor are suppressed. The unit comprises an enclosure having an air inlet through which an outside air is introduced into the enclosure and an air outlet through which a cleaned air is emitted or discharged from the enclosure; a chemical filter mounted in the enclosure to remove chemical substance existing in the outside air; a dust filter mounted in the enclosure to remove dust existing in the outside air; a fan mounted in the enclosure to introduce the outside air into the enclosure through the air inlet and to emit the cleaned air to outside of the enclosure; and a bypassing path for returning part of the outside air that has penetrated the chemical filter to an upstream side of the fan without penetrating the dust filter. A damper may be additionally provided in the bypassing path for adjusting the amount of the outside air returned to the upstream side of the fan. Preferably, the damper is adjusted in such a way that the velocity of the air at the air outlet of the enclosure is set at a specific value.
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