Clean rooms are an integral and necessary part of many manufacturing operations. The goal of a clean room is to provide an environment without airborne contaminants including common dust, aerosols, particles and other contaminants that are suspended in the air everywhere around us. Although we are relatively unaware of these contaminants in our everyday lives, most of us have wondered at the amount of stuff that is revealed in a shaft of sunlight streaming in through a window in a darkened room or in the beam of a bright theatrical spotlight.
These airborne contaminants can wreak havoc with critical manufacturing operations for optical, semiconductor and other products and must be eliminated by excluding them from manufacturing areas. On the other side of the coin, clean rooms are also employed to contain and prevent the release of things including bio-hazards and toxins present in operations including the manufacture of certain chemicals and pharmaceuticals as well as instances where there is the potential for the release of infectious diseases, for example. In this case, the goal is to contain rather than exclude things that may be floating in the air.
In either of the above cases, the clean room is an area that is carefully isolated to prevent the unintentional exchange of the air and associated contaminants inside the clean room with that in the surrounding environment. Every path for potential exchange must be sealed to prevent this from happening. The air inside the confined space is then filtered and slightly pressurized with additional filtered air to remove any pre-existing contaminants and assure that there is no unintentional inward flow of contaminated ambient air.
So far the thing seems pretty simple, no? Well, not really. In order for the clean room to be of value, materials and personnel need to enter and exit without introducing additional contaminants airborne or otherwise. The biggest potential violator here is personnel as the average human sheds on the order of one million particles a day (give or take an order of magnitude depending on the source of information you reference) mostly comprised of dead skin cells. There is also the issue of respiration which unavoidably produces both aerosols and particles. This is in addition to the contaminants introduced by parts being processed and the unavoidable shedding of particles by surfaces in the clean room. To prevent the introduction of contaminants to the clean room via these sources, entry and egress of materials and personnel is accomplished using air locks or vestibules. An air lock is a separate isolated chamber with one access connecting to the outside environment and a second connecting to the clean environment in the clean room. It is in the air lock area where parts are decontaminated before they enter the clean room and where personnel “suit up” in garments especially designed to not shed particles and prevent the escape of particles generated from within. Clean room garments range from a simple smock to the proverbial “bunny suit” which totally isolates the wearer and may even include self-contained breathing apparatus similar in function to that worn by deep sea divers.
In addition to all of the above, certain rules and procedures must be observed in a clean room to maintain the cleanest air possible. These include the prohibition of eating, smoking, wearing of makeup, rapid movements etc. as well as the enforcement of a strict regimen of continuous cleaning including the wiping down of equipment and vacuuming using special vacuum cleaners with filtered exhaust. In short, a clean room is more than a physical structure meeting certain requirements – it is a culture of discipline and fastidiousness in the extreme. The “enemy” is by-in-large invisible and ever present. In upcoming blogs we will address the purpose and function of clean rooms as they relate to industrial cleaning technology.
– FJF –