Anyone that works in cleanroom management understands what a cleanroom is. What they might not get is how cleanroom classification works. It seems, even for people who work in cleanrooms all day, every day, what constitutes them and how they are classified is a mystery. Here is a brief summary of how the cleanroom classification system works.
Every cleanroom has a baseline in terms of acceptable levels of exposure or contamination. A room where medical instruments are packaged, for instance, has a default threshold that is its classification. In the case of a medical instrument packaging lab, for example, the default is “Class 10,000” or ISO 7.
To get the proper cleanroom certification designation, three questions are asked: What are the sources of contamination, what size particles need to be filtered out, and how much air will it take to remove the contaminants?
The size of the particles that need to be filtered out plays a major role in determining a cleanroom’s classification. Specifically, when people determine that they need less than 1,000 particles per square foot, they also must factor in the particle size. A larger particle, regardless of the square inch classification, can increase the threshold of the ISO classification.
Circulation also plays a major role in determining classification. Any time a classification drops—say from an ISO 8 to a 7—twice as much air needs to circulate to achieve the same result. This reality is a major factor in determining the cost of maintaining the cleanroom and affects everything from the number of filters to the amount of air conditioning needed to cool the return air.
A Common Mistake
A common error in calculating the size of a cleanroom, and thus affecting its ISO classification threshold, is overestimating how much height is needed. If a room needs 8 feet of clearance but to even out the aesthetics of your workspace you decide to go with a 10-foot ceiling, that adds 25 percent more to the overall cleanroom operational estimate. You will need 25 percent more air and the associated particle contamination controls, including filters, HVAC, and air conditioning power. All of that adds significantly to the overall unit operational cost. Multiply that by several cleanrooms and you have a significant, unneeded cost associated with your cleanroom that must be addressed, or something must be sacrificed. Your cleanroom should be exacting in the required size and, from that, you can build the other requirements.
Cleanroom classifications can be confusing to most people, even those who work in cleanroom management
. Often, they think they know how a room will be classified but overlook key elements that affect its ISO rating.