by Hank Rahe
 |
Based on what I have seen in most applications of contamination control containment devices, it would appear that suppliers are not asking the basic questions: “What activities are going to take place within the device? How will users need to interact with the equipment contained in the device?” Or, is it that the users of these devices are unable to explain their activities to the supplier.
The major problem in the selection of the proper contamination control device for a specific job is that in many applications, the device is either badly designed or does not have the capability of achieving the level of control required. The misuse of the device could be construed as a user problem, due to a lack of understanding of what to use, but the responsibility for defining the capabilities of contamination control devices should fall to the suppliers of such devices.
Could the problem be that companies are selling what they have rather than what the customer needs? Suppliers who take this approach leave a trail of dissatisfied customers and lose repeat business. In this industry, customers talk to each other frequently and do check references.
Fume hoods are the classic example of such misuse. These devices are used in laboratories for weighing powders and other particle control functions, with seemingly no consideration given to the fact that the name of the device may be some clue as to its intended use. The capabilities of these hoods are not well defined, and no testing standard exists. Most testing experts admit that there is no means of determining that the units are functioning properly for a given application. In many cases, the units create a false sense of security and present a significant danger of exposure not only to the individual using the unit, but also to others working in the environment.
Type II biological safety cabinets are also used for a variety of applications without consideration of their capabilities. These units were designed and tested to NSF 49 standards, which clearly do not establish particle control capabilities. Recent studies conducted by several sources in pharmacies and laboratories have shown particle contamination existing outside the confines of these cabinets. The dynamics of activities for which the units are used clearly exceeds their capabilities if containment levels in the low microgram range are required.
Many times, the source of confusion comes from the transference of the intent of the control device, be it gasses, liquids or solids, to a general “one size fits all” mentality. The thinking may be that if the contamination control device works for gasses, will it not work for solids too? Containment of particles is where this problem occurs most commonly, because most applications involve a variety of different materials and have different particle sizes, shapes and bulk density. If data were available indicating capture velocities, the user would have to profile the materials and communicate the specific characteristics of the material to be contained.
Testing the capability of the device to contain the powder, by using a marker powder, is only effective if the material used in the testing simulates the actual characteristics of the powder. The purpose of using the marker powder is to assure that the materials will have an assay method or can be visually detected. A typical improper use of testing materials is using “smoke” to show directional movement of particles. The “smoke” will not emulate the solid particles, in terms of the effect that the airflow has on their movement. Testing reduces or eliminates subjective judgments regarding effectiveness of the device and replaces them with data only if the testing reflects the actual materials to be used in the contamination control device.
Hank Rahe is director of technology at Contain-Tech in Indianapolis. He has over 30 years' experience in the healthcare industry, as well as four years in academia. He is an expert in the areas of conventional and advanced aseptic processing. He is the past chairman of the board of the International Society of Pharmaceutical Engineers, and is a member of the CleanRooms Editorial Advisory Board.