design, which we will now explain through an example. Typically, low moisture medicinal products such as tablets or capsules are dry and dusty, therefore more likely to be a significant cross-contamination risk. If the “clean” area pressure differential was positive to the corridor, the powder would escape out of the room and enter the corridor, and is likely then to be transferred into the next door cleanroom. Thankfully, most dry formulations do not readily support microbial growth, so as a general rule, tablets and powders are made in “clean corridor” facilities, as opportunistic microorganisms floating in the corridor don’t find environments in which to thrive. This means that the rooms are negatively pressurised to the corridor.
For aseptic (processed), sterile, or low bio-burden and liquid medicinal products, the opportunistic microorganisms usually will find supportive media in which to flourish, or in the case of an aseptically processed product, a single microorganism could be catastrophic. So these facilities are normally designed with “dirty corridors” as you want to keep potential microorganisms out of the cleanroom. Unlike powders, droplets of liquid don’t generally “leap up” and float around the facility.
Designs can become complicated if the products or raw materials are highly potent, which cause occupational health and safety issues, or if there is a need for biological containment. These are outside the scope of clean room basics, reading this blog on dedicated facilities could assist. If you need help from our clean room designers can help.
Which way should my clean room doors swing?
Unless you have power-assisted doors, all doors should open into the room with the higher pressure. Double-leafed doors are notorious for causing the pressure differential balancing of rooms to drift off as the door springs gradually weaken and the doors leak air between rooms at levels outside of the design parameters.
Annex 1, Clause 47 specifically states that sliding doors are not permitted in sterile plants as they typically create uncleanable recesses, projecting ledges and recesses. For these reasons they should not be used in non-sterile facilities either.
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