by Ken Goldstein, Ph.D.
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In recent columns, we looked at the subject of cosmetics in cleanrooms because some people are again asking if it is ok to wear these substances inside contamination-sensitive areas. The short answer was “no,” with moisturizing lotions for those people with dry flaking skin as the only exception.
The reason behind the requirement of “no cosmetics?” The first rule of contamination control: never bring anything into the cleanroom unless it absolutely has to be there.
By the mid-1980s, the early research was completed and the results were published (see “Cosmetics in Clean Rooms” by Phillips, Auser, Meikel, Baldwin and Washington, Proceedings of the Institute of Environmental Sciences, 1984, p. 317-323). If anything, these results were worse than anyone suspected. The research identified 15 elements and 48 compounds in commonly used cosmetics. The average number of particles (0.5 micrometer and larger) contained in a typical facial application ranged from 82 million for eye shadow to a high of three billion for mascara. The total particle number of particles was more than five billion per facial application.
Note that all of the particle numbers described above were for particle diameters greater than or equal to 0.5 micrometer. If we were to perform this research today, we would certainly look at particle sizes down to 0.1, probably down to 0.05 and possibly as low as 0.02 or even 0.01 micron. With this range, we would expect to see at least an order of magnitude (10x) increase in the particle numbers.
Perhaps coincidentally, another article appeared at exactly the same time: “Contamination of Technological Components By Human Dust” (E.W. Moore, Proceedings, Institute of Environmental Sciences, 1984, p. 324-329). This research provided a description of skin cells and their functioning along with their chemical composition, noting that skin cells are highly insoluble and resistant to heat. In other words, they are difficult to wash off, dissolve off or burn off.
In effect, Moore did for human skin what the previously mentioned paper did for cosmetics. It explained to the engineering community how skin was capable of causing significant chemical contamination of a broad range of sensitive products. It also helped to explain the sole exception to the no cosmetics rule (moisturizers for dry flaking skin).
For people involved with pharmaceutical products, this whole issue was as troubling as it had been to their cohorts in the microelectronics field. While pharmaceuticals are generally much less sensitive to chemical contaminants than microelectronics, they are much more sensitive to microbiological contaminants. Skin cells combined with cosmetics create an especially risky combination. Cosmetics are suspect not only because of their chemical constituents, but also because they tend to slough off and carry bacteria and other bio-burden with them. Combine this with the microbiological contamination inherent within human skin cells and the problem of maintaining cleanliness and sterility comes into focus.
Necessary evil
Now let's consider something that is definitely not politically correct from a contamination control perspective. At some time in the not-too-distant future, say within 10 years, we may relax or even drop this ironclad “no cosmetics” rule. And while 10 years can be a very long time in this fast-paced business, most of us will be around to see it.
Recall that cleanrooms are highly artificial environments with strict rules governing gowning, production activities and behaviors. Working inside a cleanroom has been described as challenging, confining, hot, difficult and claustrophobic. The astute reader will have noted that the word “fun” is not included in this list. Cleanrooms are most definitely not fun places in which to work. Unfortunately, the stringent controls on people's behavior and gowning are necessary to protect the product and process. But what is now may not be in the future.
In the mid-1980s, a “new” technology was added to the contamination control tool kit. Eventually called “minienvironments” by the microelectronics people and “barrier/isolation technology” by the pharmaceutically oriented, the new technique started with the revolutionary but obvious premise that the product and process occupied only a small portion of the cleanroom while the vast majority of the space inside the clean facility never “saw” the sensitive things that drove the area cleanliness requirement.
Using this Pareto Analysis starting point, one question jumped out: why bother making the entire cleanroom ultra-clean? Why can't we just use some type of physical barrier to enclose and protect the critical space immediately surrounding the product or process and then let the rest of the room drift to some particle cleanliness level less stringent than required in the sensitive area?
It has certainly taken us a while to implement this technology, but we have made significant advances in the past few years and are almost certainly heading in this direction. Now imagine some point in the not-too-distant future when process automation, barrier and isolation technology and minienvironments are sufficiently advanced to effectively remove the human operator (and his/her debris) from the immediate environment surrounding the product.
Two possibilities come to mind:
- The cleanroom will be completely automated. With this development, we might suggest that people are no longer required inside the room and the no-cosmetics rule can be discarded. Admittedly, this is a reach. What about maintenance activities? Can we expect this to be completely automated too? And never forget that these expensive facilities must take into account that Murphy is always out there, looking over our shoulders and taking a keen interest in our affairs. But full automation is still a possibility that we cannot fully discount.
- If the minienvironment and barrier/isolation technology truly lives up to its potential, we may not really need a cleanroom. If the isolation technology is good enough, people will be able to enter the room without gowning and with no behavioral restrictions. We are certainly not there yet, but we are clearly moving in this direction.
Because minienvironments and isolation technology will be a critical part of the future of contamination control, we will look at this in more detail in upcoming columns.
Dr. Ken Goldstein is a principal with Cleanroom Consultants Inc. (Scottsdale, AZ) and is a recognized expert in planning and designing of cleanrooms and ultrahigh purity systems. He has been associated with the cleanrooms industry for 20 years, and is a senior member of the IEST. He is active in WG-012 (Cleanroom Design) and WG-028 (Minienvironments).