This standard stipulates clean benches () that have built-in blowers and HEPA or ULPA filters to maintain a certain level of air cleanliness (hereinafter referred to as cleanliness) in the work space. However, this does not apply to structures where the work space has a negative pressure. Note () Also applicable to tunnel units, fan filter units, and clean booths. Regarding the fan filter unit, please refer to the annex (regulations).