Problems establishing environmental control in nonhazardous drug buffer rooms can be related to misunderstanding the room’s airflow and proper placement of the PEC.
The diagram below shows the perfect scenario for placement of a PEC in a positive pressure buffer room, while taking airflow into considerations. Of course, this is not the only acceptable approach but it is the optimal approach and should be taken into consideration if there are issues with environmental control.
If a buffer room, arranged in a different manner, is not experiencing issues with frequent viable excursions and passes certification, while all under dynamic conditions with the most people present, then the room is functioning appropriately. (Important to emphasize viable testing and certification conducted under dynamic conditions and when the most people are actively working). However, if there are reoccurring issues, if there is a desire to improve the environment or in the market for renovations/rebuild then the diagram below should be taken into consideration.
In the diagram, the PEC is located on the cleanest side of the buffer room, ceiling HEPA filters are located in front of the PEC (but not so close as to disturb air current) and low air returns are on the opposite wall (the dirtier side of the buffer room and also where the entrance to the room should be located).
The GREEN arrows depict HEPA filtered airflow. Note the airflow that is coming out from the PEC, moving outward and away from the most critical area, the direct compounding area (DCA). Next, notice the GREEN arrows moving downward from the ceiling HEPA filter. If a compounder were standing in front of the PEC, this combination of airflow would direct any particles out and away from the PEC and down to the floor, as shown with the BLUE arrows. Finally, the low air return and the prefilter of the PEC pulls air out of the room and recycles the air back into the room through HEPA filters, removing particles of 0.3 microns or larger (YELLOW and RED arrows).
Again, this is an ideal scenario with consideration to airflows. Some rooms work quite well with different setups (e.g., low air returns at the sides). The key is to establish environmental control shown with viable testing and successful certification under dynamic conditions with the most people present. If a room with a different setup is not experiencing issues then the room is functioning as needed. However, if a facility is experiencing issues or frequent viable excursions then it may be time to consider rearranging the buffer room upon the next certification.
Note: Once compounding spaces are altered, recertification is necessary therefore have your certifier on notification.
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