Please note:
This article is very similar to “Three different types of cross contamination control utilized in Airlocks”.
As a pass through hatch is effectively an airlock for product. With airlocks there are three different types of pass through hatches there are two different types.
They are bubble and cascade.
Bubble
Summary
A bubble airlock is one with a positive pressure in relation to the internal and external zone.
Why it works
Because it runs at positive pressure to both areas it creates a barrier where contaminants within either area are pushed back into their own respective areas.
Application
Used in, areas where the products needs protection and the people external to the cleanrooms require protection from the product, to reduce the possibility of viable articulate from entering the lesser pressure cleanroom. Areas such as high potency, compounding areas where terminal sterilization is not an option.
Important considerations
The air being used to pressurize the bubble needs to be of higher quality than both the internal and external zone.
Because of the air tightness of a pass to hatch a specific bleed point is required, and this is usually located on the external zone or lower grade area to “wash” the product in the first pass air from a terminal filter.
By adjusting the volume of air supply and the amount allowed to be released from the through hatch the pressure of this pass through hatch can be controlled, due consideration needs to be given to the pass through hatch construction methods and installation techniques as over pressurization can be the cause deflection in doors resulting in seals (particularly if rub seals are employed) resulting in the past through hatch no longer being able to hold pressure, increasingly the leakage rate from the cleanroom, causing pressurization problems, requiring more power to operate your cleanroom, and depending on the type of cleanrooms being operated a possible entry point for viable and non-viable particulate.
Cascade
A cascade airlock is one where the positive air pressure flows from the high-pressure internal zone to be airlock and from the airlock to the lesser lower pressure grade area.
Summary
Cleanroom air flows from the clean room to the airlock and from the airlock to preparation areas.
Why it works
The cascade effect keeps the particulate external to the critical area.
Application
Any manufacturing facilities where the product requires protection from particulate but the people outside the clean room do not need protection from the product in the cleanrooms.
