by Hank Rahe
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A contamination control system consists of engineering controls, work practice, administrative controls and personal protective equipment. To find solutions for contamination problems that work for you and are cost effective, it's imperative to understand each of these four elements and how they must be combined to achieve the desired result.
Any successful system requires all four elements. Evaluate your total system to determine what combination will achieve the desired contamination control level.
The cause of contamination and where it occurs defines the problem. In finding a solution for the problem, a combination of the four elements must be carefully considered.
Each of the four elements has limitations and needs support from the others. Engi neering controls are the most in dependent, when properly in stal led. However, poor work practices and ad ministrative controls can negate the effectiveness of the engineering controls.
The selected engineering control must have the capability of containing to the required level of exposure control, but is still dependent on the other elements to be successful. Some engineering controls require more support than others, which places an additional burden on the other elements.
Directional airflow devices require support from all elements. For example, the Class II biological safety cabinet requires excellent work practices within the contained space, cleaning methods for the products removed and personal protective equipment.
The same support elements for a properly designed barrier isolation technology system are not as demanding; thus, barrier isolation technology is much less dependent on the other three elements. Although operators must learn the proper way to insert and remove materials, the use of waste disposal chutes and carriers for the exiting product provide protection and reduce the potential for exposure to the very low nanogram range.
In routine operations, personal protective equipment is reduced to secondary protection, such as the use of gloves in handling the containers of the end product.
The dependence on any element, other than engineering controls, means the human element is actually in control of the containment capability. Any activity, such as making connections, movements within the critical zone in the containment device or removal and disposal of materials, adds to the risk of exposure. Having engineering controls in place that are less dependent on these activities being completed without errors will reduce risks.
Many times administrative controls are used when the engineering controls and personal protective equipment are not adequate to protect to the exposure level required. In this case, the exposure time for personnel is limited in order to keep employees within the acceptable limit of exposure.
This approach is used for exposure to radiation and hazardous materials, if the engineering control is incapable of containing to the point that a short-term exposure will not exceed the set exposure limit. The individuals working in the area are limited in the amount of time or number for repeated exposures.
This approach is expensive because many times it requires additional employees working fewer hours. It is important to understand the ability of the body to recover from the exposure through the natural elimination of the radiation or chemical from their system. If there is an accumulative effect this must be taken into account in determining the level of exposure time.
Evaluate your total system to determine what combination will achieve the desired contamination control level.Because they are less dependent on people to consistently perform a given operation prop erly, engineering controls provide the most dependable means of achieving the proper level, but cannot work without some level of involvement from the other elements.
Hank Rahe is director of technology for Containment Technologies Group and is a member of the CleanRooms Editorial Advisory Board.