by Robert Powitz
My introduction into the world of cleanrooms was through the science of biological safety, where the emphasis is on protecting people. The biological safety paradigm is: keep organisms from getting out; contain the ones that have gotten out and minimize the movement of those that were not contained.
The biological safety paradigm is: keep organisms from getting out; contain the ones that have gotten out and minimize the movement of those that were not contained.
In practice, we rely on the Class II biological safety cabinet as the most important tool in providing a primary barrier between an infectious organism and human contact. We know through experience and a wealth of epidemiological data and applied microbiological research that a well-maintained biological safety cabinet, when used in conjunction with good microbiological techniques, provides an effective containment system for safe manipulation of moderate- and high-risk microorganisms.
If needed, we further minimize risk of infection when dealing with the most virulent pathogenic organisms by placing the biological safety cabinet in a containment area that is specifically designed to keep any escaped organisms from outward migration. This is achieved by a combination of dilution ventilation and air locks to maintain the directionality of airflow. In high-containment facilities, both the room air-supply and exhaust are HEPA filtered. Therefore, in those facilities categorized as Biosafety Levels 3 and 4, the rooms can easily meet ISO Class 5 cleanroom criteria.
Although this is a rather abbreviated description of biological containment, the central theme is that biological safety relies on HEPA filtration to capture aerosols containing infectious particles, and, the biological safety cabinet is universally used as the basic primary barrier for any manipulation that may present a risk of possibly generating a bioaerosol.
Simply stated, the classic biological safety cabinet is an excellent example of a mini-environment and barrier isolation technology and the containment facility is a cousin to the cleanroom.
This idea is also the driving force behind some of the cleanroom applications in the food industry. In both biological research and food production, the concern with cross-contamination, generally from a wet aerosol source, is adressed in much the same way.
However, over the past few decades, biological research and food production have started relying on the same facilities to provide both a barrier against cross-contamination and a “clean” environment for the protection of the research or the finished food product. Needless to say, this conundrum has resulted in some interesting design applications where biological safety cabinetry and clean benches share the same area.
So it is with certain processing and fill operations in the food industry. Mini-environments and barrier isolation technologies (primary containment) control both raw food processing and packaging of the finished product within the same cleanroom environment (secondary containment) and without the benefit of a separating wall or building (tertiary containment).
Where this type of facility is planned, several approaches and techniques of control should be established. Keep in mind that all design should conform to current good manufacturing practices (CGMPs). Among the most critical for biological control are the following six criteria:
- Rely on primary containment by using mini-environments and barrier isolation technologies to contain microorganisms at their point of use or to exclude them from specific work areas.
- Establish traffic patterns along a clean-contaminated axis for both the product and people. This should also include providing change rooms for personnel that are contiguous with the cleanroom area and complement the clean-contaminated axis traffic pattern.
- Use differential air pressures within a facility or sub-facility so that air moves from biologically clean areas toward areas of higher microbial contamination. Use air locks and door barriers to separate areas of unequal and unusual microbiological loading or risk.
- Use cleanroom technologies, specifically the application of appropriately effective microbiological filtration or other treatment for air supplied to and/or exhausted from rooms, areas and processing equipment.
- Provide for in-place cleaning as well as facilities for conventional cleaning within the production facility. Also provide for the treatment of microbiologically contaminated liquids and solid wastes taken from the area.
- Use an effective intercommunication system in the facility to avoid unnecessary movement of personnel from area to area.
Cleanroom technology has a definite role in the food industry. It complements, and may actually become necessary to meet the criteria set forth in CGMPs, hazard analysis critical control point (HACCP), and most recently, food security programs.
The approaches to the design and use of cleanrooms in food manufacturing are similar to that used in biological safety. Applying the paradigms of biosafety with this new application will ensure success for the industry, cleanroom manufacturers and providers of third-party oversight.
Editor's Note: “Unfiltered” has quickly become one of the most popular monthly features. In an effort to give our readers more voice, I'd like to put the direction of this column in your hands for 2002. What issues would you like to see explained, argued or demystified? Drop me a line at [email protected].