In a work performed in a clean atmosphere such as a work in a manufacturing stage of a semiconductor and an electronic component or a work in a manufacturing stage of pharmaceuticals, for example, the work is performed in a clean work environment where the inside is kept in an aseptic and dustless state so that contaminants do not intrude from the outside environment. If the work environment in which such work is performed is small-sized, an isolator device in which a chamber or the like sealed from the outside environment is used and a worker can perform the work through a glove or a half suit from outside this chamber is used. Such isolator devices are particularly called aseptic isolators.
On the other hand, a work handling a substance affecting a human body such as a work in a manufacturing stage of pharmaceuticals, a work handling highly toxic microorganisms in the medical and biological fields or a work handling radioactive substances, for example, it is necessary to protect the workers from contamination of chemical substances, microorganisms and the like affecting a human body or to prevent leakage of these chemical substances, microorganisms and the like affecting a human body from the work environment to the outside environment. In such works, the isolator device in which a work can be performed through a glove or a half suit from outside the chamber sealed from the outside environment is used. Such isolator devices are particularly called containment isolators.
The isolator device is shielded from the outside environment where workers perform a work in an airtight manner, purifies outside air by a filter and supplies it into the chamber and also purifies the air in the chamber by the filter and discharges it to the outside. Therefore, such isolator device can be also used basically both as the aseptic isolator and the containment isolator.
Moreover, when the isolator device is to be used, safety can be further improved by adjusting an air pressure in the chamber in accordance with the purpose. That is, when the isolator device is used as an aseptic isolator, the pressure in the chamber is set to a pressure higher than an outside air pressure (hereinafter referred to as a positive pressure), and even in the case of leakage from the chamber, since the air flows from the chamber side to the outside, airborne bacteria and the like are prevented from intruding into the chamber from the outside
On the other hand, if the isolator device is to be used as the containment isolator, the pressure in the chamber is set to a pressure lower than the outside air pressure (hereinafter referred to as a negative pressure) in use, and even in the case of the leakage from the chamber, since the air flows from the outside into the chamber, the chemical substances and the like in the chamber are prevented from contaminating the outside environment.
However, in the isolator device, a glass window through which the inside of the chamber can be visually checked from outside, a glove with which the worker performs the work, and an opening/closing door by which equipment is carried into the chamber or maintenance works are performed are provided. Therefore, it is difficult to completely shield the chamber of the isolator device in an airtight manner, and the shielding performance might be destroyed during operation of the isolator device. Moreover, even if the air pressure in the chamber is adjusted, there is limitation in providing a pressure difference all the time due to various factors such as fluctuation of the outside air pressure.
If any leakage is caused in the isolator device as above, in the aseptic isolator, the aseptic/dustless state in the chamber cannot be maintained, while in the case of the containment isolator, the chemical substances, microorganisms and the like handled in the chamber might leak to the outside environment.
As a method for avoiding such a risk during operation of the isolator device, Patent Literature 1 discussed below proposes a cleanliness maintaining device of an isolator device in which a negative pressure air suction passage whose pressure becomes negative both to the inside of the chamber and the outside is installed on an inner peripheral edge of a joint portion provided in the chamber, and the air passing through the inner peripheral edge of the joint portion is sucked by the negative pressure air suction passage.
On the other hand, works accompanying risks after the operation of the isolator device finished include a work of replacing a used filter. For example, in the containment isolator device, the chemical substances and the like in the air are removed via the filter for purifying the air therein and the purified air is discharged to the outside environment. As a result, leakage of the chemical substances and the like handled inside the isolator device and the like to the outside environment is prevented.
As such filters for purifying the air, high performance filters such as HEPA filters and ULPA filters are used, and a large quantity of the chemical substances and the like removed from the air adhere to the used filters. Therefore, when these used filters are to be replaced, a careful work is required for protecting safety of the worker and for preventing leakage to the outside environment.
A method employed most widely in this filter replacement work is a bag-in/bag-out method, but in this prior-art method, a structure of a housing accommodating the filter becomes complicated, and the filter replacement work becomes cumbersome.
Moreover, the inside of the housing is divided by the filter, the chemical substances and the like adhere to a surface on the upstream side of the filter along the air flow, while a surface on the downstream side of the filter is not contaminated. In such a state, the used filter is removed from a mounting plate in the housing and accommodated in the bag, but there is a concern that the chemical substances and the like adhering to the surface on the upstream side of the filter contaminate a downstream portion of the filter in the housing in a stage until the filter is accommodated in the bag.
If the downstream portion of the filter in the housing is contaminated by the chemical substances and the like as above, the chemical substances and the like having contaminated the downstream portion of the filter in the housing might leak to the outside environment when the isolator device and the like is operated after the filter replacement.
As a method for avoiding such risk, a safe filter housing replacing method is proposed in Patent Literature 2 discussed below in which the housing accommodating the used filter is removed with the housing and replaced by a new housing accommodating a new filter.
In this filter housing replacing method, the air in the room such as the isolator device is sucked through an air inlet opened on the housing upper face, the air is purified by a filter accommodated in the housing, and the purified air is discharged through an air outlet opened in the housing side face. Here, the housing air inlet is detachably connected to an insertion port of a work chamber of the isolator device and the like, while the air outlet of the housing is detachably connected to a discharge-side duct.
When this housing is to be replaced, first, a filter upstream portion which is a contaminated portion in the housing is sealed by placing a lid on the air inlet on the work chamber side of the isolator device and the like. Subsequently, the inside of the work chamber is washed and then, the air inlet of the housing is removed from the insertion port of the work chamber. Moreover, the air outlet of the housing is removed from the discharge-side duct, and the lid is placed thereon.
With this filter housing replacing method, the filter replacement work is relatively easier than the prior-art bag-in/bag-out method, and risk of contaminating the outside environment during the removal work of the housing can be reduced. Moreover, since both the air inlet/outlet of the removed housing are sealed, the outside environment is not contaminated.