Cleanroom cleaning is a maintenance service unlike any other. Although it is still common to hear people refer to it as janitorial service, there are few similarities. For instance, let's compare it to some other common forms of maintenance: lawn, parking lot and office maintenance. These all share similarities in that a job well done is evidenced in a visual inspection. Is the grass trimmed neatly? Is there debris on the parking deck? Does the desk have dust on it? One simple inspection reveals the effectiveness (or ineffectiveness) of the service.
This stands in stark contrast with a cleanroom in which visual inspection has limited value. In fact, a dirty cleanroom should look better to the human eye than any room recently cleaned outside the cleanroom. This is because the cleanroom environment is mechanically designed to reduce visible contamination. Cleanroom cleaning addresses the insidious particulates that dwell beyond human vision. Thus the disciplines required for cleanroom cleaning are not the same for those mentioned above.
Another important consideration is that cleanroom cleaning has a direct effect on company revenue. Few involved in lawn care or bathroom cleaning can have an impact on company profit! Thus greater attention should be given to determine the effectiveness of cleanroom cleaning that directly impacts production.
The number one issue on the subject of cleanroom maintenance concerns the effectiveness and application of the cleaning process. And because visual inspection is insufficient, cleanroom maintenance workers must rely on analytical tools.
The development and maintenance of this data – along with a practical application of the cleaning process to the cleaning technicians – requires strong management oversight. The knowledge set and how to apply it practically while managing the work force requires more than supervisory skills. Cleanroom cleaning is the marriage of science and practical application to the work force, which is no easy job.
In addition to the inspection and auditing tools used in cleanroom cleaning, other factors also influence the effectiveness of cleanroom cleaning:
- various applications
The hub from which all of the various spokes of services are applied comes from an on-site management team. This can be as small as one person who both manages and cleans the room or as large as a full-fledged team with levels of supervisors, crew chiefs, and a host of technicians.
Cleanroom site managers need to be the librarians of all the data that compose a competent cleanroom program. These include:
- effective cleaning procedures
- a list of approved cleaning equipment, tools, wipes and chemicals (including dilution rates)
- safety procedures
- protocol instructions
- production information (shifts, special situations)
- shift schedules and
- employee information (such as specific certifications for specific duties i.e. ladder, enclosed areas, subfloor, etc).
This and other pertinent information should be readily available to cleaning technicians and their supervisors so that all can see the depth and breadth of the cleaning program. Managers should make regular tours of the facility to observe and audit cleaning practices and their effectiveness. The on-site manager then becomes a single point of contact for other department managers to communicate contamination control issues.
The key to setting up and maintaining a complete contamination control program rests on the ability to inspect and audit the process. Inspection of the cleanroom surface should be performed both before and after cleaning. The collection of this data helps determine the effectiveness of the cleaning process. In addition, it points to tool, wiper and chemical dilution rate effectiveness.
The data should be collected and tabulated as part of an on-going cleanroom audit process. Unlike the case with the IRS, you will be glad to have this regular update to keep you informed, honestly, as to the effectiveness of your contamination control program.
There are several ways to inspect a cleanroom surface to determine the effectiveness of the cleaning. One tool is the QIII. This tool reads particulates on surfaces and tabulates the data for analysis. [Note: The QIII cannot read particulate that is bonded to the surface by electrostatic or van der Waals' forces.]
By taking readings before and after cleaning, this tool assists the operator to see the effectiveness of the cleaning process.
Other tools include:
- White oblique lights
- Black lights
- Wipe test (black and white wipers)
- Ferrous metal tests
Note that all tests that rely on visual inspection are effective only on particulates considered gross contamination (above 50 microns). Visual inspection of cleanrooms does have value – large amounts of particulate have been identified with the naked eye. But the real issue is that visual inspection gives only a very small picture of the true level of contamination in your cleanroom.
Once effective test methods reveal the optimal cleaning process, regular surface inspection should be used to determine particulate return to each surface. This data will form the on-going basis of your cleaning program and the necessary frequency for contaminant removal. Keep meticulous data as to what, when and where you found the particulate. This audit, after time, will serve as a blueprint or even a fingerprint of your room's particulate return to surface. Because most inspections are subject to human error, the longer you record your findings the more you can eliminate the noise in your data.
Tools of the trade
Working closely along with the audit process is the right choice of tools to perform the cleaning service. Just how important these are can be illustrated by the automated car wash. Years ago many of us were happy to use the automatic car wash. In contrast to our spending half of our Saturday afternoon washing and waxing the car we could now simply drive up and let modern machinery do the work. From the window we watched our car go through each process: Soap and water, brushing, rinsing, waxing. At the end of the line a bright shiny car. It took some time for us to see the fallacy of this service. Because soon we observed, and I might add a little too late, tiny scratches in our paint. These soon gave way to a rough surface that made the car harder to clean and unsightly. What happened? While we stood behind the glass in the safety and comfort of the waiting room…our car was being wiped by tiny nylon lines similar to the ones found on weed wackers. These rotating brushes removed the dirt but at the same time slowly damaged the topcoat of our paint.
The same is true with cleanroom cleaning. For years janitors brought into our cleanrooms the same technology used in office cleaning. Such tools as the roller brushes flopped or whipped the cleanroom surface. Cleanrooms operate best when the laminar airflow is disturbed as little as possible.
The right tool for wiping cleanroom surfaces is one where the process of absorption is applied. These tools should address as large a surface as possible. This will limit our strokes and clean the greatest amount of area while limiting movement in the air stream. Several designs exist that employ a paddle and wiper combination. These work well on large surfaces such as floors and walls. Smaller areas such as ceiling grids, tables, ledges, gowning bins, and door handles require hand wipes. Fortunately the same technology that makes one effective works on the other.
A key to effective cleaning is the proper mixture of chemicals and DI water to the wiper. This is the basis of absorption. Not enough liquid and little particulate absorption will take place. This may also cause abrasion from one dry surface to another. Too much liquid will leave undried residue that stores particulate on the surface until it dries.
Currently a great deal of research and testing is being done on ways to dispense the right amount of liquid (whether chemical or DI) onto the wiper surface. Always observe liquid residue after wiping a surface. Time the evaporation. Try to reach liquid application levels to meet the minimum amount of drying time.
Not all surfaces in the cleanroom require the same process. Seamless floors require one process, metal-plated grid floors another. Some areas require pre-vacuuming and others do not. Here's where testing each surface regarding the effectiveness of the process and return of particulate to surface will determine how and when you will clean them. Nowhere greater is this need than in cleanrooms where bio-burden is a factor. In addition to specific practices regarding kill rates and dwell times, an effective cleaning process requires testing to determine which process is best and how often it is required. Once again test, test and test!
Once you have determined an effective cleaning process use the data you are collecting in your regular cleanroom audit to determine the optimum cleaning schedule. Here's another analogy: Homes with children have different cleaning schedules than those without. Rooms with little feet and hands tend to require more attention than those that stay closed. The same is true of your cleanroom. How many people use your room? How do they gain entry? Follow the 'trail of contamination' that stems from your gown room to the process area. This source of cross contamination requires more attention than less traveled areas. On the other hand, rooms or areas within your cleanroom that have special requirements may require the greatest attention.
Cleanrooms create revenue. And within the cleanroom there are specific areas where the revenue is generated. This area needs the most attention. More time should be spent in ridding particulate that is adjacent to process than anywhere else. Keep in mind that surface contamination near product is only an air turbulence away. All it takes is one event and surface contaminant is airborne.
One important area where cleanroom maintenance is different from other maintenance services is regarding safety. In most cleanrooms there are processes underway that include dangerous chemicals. These need to be treated with care. No cleaning program can be administered without the education of what constitutes a dangerous situation. Along these lines cleanroom cleaners should know how to evacuate the building in case of fire or other emergency circumstances.
The continued education of cleanroom cleaners on the cleaning process and how it relates to the product that the cleanroom supports is also very important. Each cleanroom has a particular reason for its existence – unlike offices where there is a generic use of space. Cleanrooms are built for specific reasons.
Cleaning should not be designed as though its function is separate from the production process. Instead, all involved in the cleaning program should understand and cooperate with production, looking at all aspects of contamination control. This, too, takes us back to the audit process, which helps us see the blueprint of our facility and how best to control contamination around the revenue-creating product. This should be an on-going process with regular updates and frequent evolution in the cleaning functions. Never should a cleaning process be so rigid to reject cleaning a special area or spill that requires immediate attention.
A great deal of thought should go into cleanroom cleaning's design and application. Companies that compete in the next millennium know today that they must do things better and faster than before. By taking this aspect of contamination control seriously, cleanroom-based manufacturing will stay on the cutting edge of technology.
Larry Mainers is founder and president of TEC International, which has provided contamination control services for cleanrooms since 1985. He is also vice president of Pentagon Technologies, which is made up of five contamination control companies: TEC International, Dryden Engineering, Biocon, Suresco, Envirosafe, and SSI.