Cleanroom design needs to take into consideration the testing of the HEPA filters, hood locations, and the return locations. Cleanrooms depend on gravity to pull heavy particulate to the floor, so low-level returns need to be placed in appropriate locations around the room to capture these particles before people enter and stir them into the airstreams. If a clean bench’s design draws air into the top of the unit, particles can be pulled into the airstream and redeposited on product that has already been sterile compounded. To help reduce this risk of this occurring, placing low-level returns in all corners of rooms, and using the door as a return as well, by not utilizing door sweeps is recommended. The use of door sweeps is a bad idea, as they cannot be properly cleaned and they cause a dead spot in front of the door. Gaskets on doors are also not a good idea as air movement is needed to provide positive pressure in these rooms.
Stay tuned for Part II in our Sept/Oct issue!