Abstract: 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.

Abstract: In an air conditioning apparatus, it includes a clean room, an air cleaning section, a cooling section and an air mixing section. The air cleaning section cleans air to supply to the clean room as cleaned air. The cooling section includes a plurality of cooling units and a plurality of non-cooling units. A plurality of cooling units cool air from the clean room to send out as cooled air. A plurality of non-cooling units sends out as non-cooled air from the clean room without cooling air. Each of the quantity of the cooled air and the non-cooled air is determined to compensate an amount of heat generated in the air conditioning apparatus and to reduce a pressure loss given to the air passing through the cooling section to a substantial minimum. The air mixing section mixes the cooled air and the non-cooled air to supply to the air cleaning section. The cleaned air is circulated through the clean room, the cooling section and the air mixing section to the air cleaning section.