Categorizing things is a method people use to survive. Searching the internet on this topic yields many interesting studies and theories about why we do it. Categorization helps us to identify a situation quickly, categorize it and act accordingly. We do it all the time. This approach rings true not only of individuals, but also with communities, businesses and industry sectors.
Defining categories for potency of pharmaceutical compounds has been invaluable to our industry. It allows R&D to evaluate and define the potency of new compounds so they may be handled safely. Architects and engineers are then able to seek the right approach for facility design with appropriate material and personnel flows as well as process design with suitable engineering controls for containment. Equipment vendors offer containment solutions, most often marketed for the common industry operator exposure level (OEL) bands: less than 1 μg/m3, 1-10 μg/m3, 11-100 and so on.
So designing process and facilities for potent compounds seems simple - until you start asking some questions. What type of material manipulations will be made? In what quantity? How often? How much does the containment device and its associated maintenance cost? Will operators be able to run the process without restriction? Is there really a difference between designing for compounds with OEL 9 μg/m3 vs. 11 μg/m3?
The answers to the above often clash with our desire to operate within the well-defined categories of potent compounds. About a decade ago, large drug manufacturers followed a prescriptive, category-based approach to designing for potent compounds. Isolators were often used for all applications if compounds were rated at 10 μg/m3 or below. A split butterfly valve of one type was suitable for a range of 1-10 μg/m3, while a more specialized, and much more expensive type was always used for less than 1 μg/m3.
Today, the design solutions we implement at IPS for processing of potent compounds depend on thorough evaluation of the operation. For example, low volume, low energy sampling activities performed a few minutes a day may sometimes occur in an open sash containment device while high volume weighing and dispensing for several hours may require an isolator for the same compound. It takes an educated and thorough design approach for potent compounds to ensure the optimal balance of safety, operability, control of risk, and cost-effectiveness.