Facility Design Contamination Control Considerations
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The following discussion describes considerations for Functional Operation of the Suite, Cleanroom design, USP Requirements and Basic HVAC Principles that must be carefully melded together to design and build a USP 797 Suite that can be certified as compliant.
The functional operation of the suite considers concepts of room segregation to establish physical boundaries between spaces for the establishment of room pressurization relationships, positive and negative, necessary to minimize migration of contamination. Critical design points for contamination control include:
- Sink location
- Hand hygiene
- Accommodations for support facility cleaning
- Ante room placement for garbing
The facility should ensure the ability to provide a safe working environment to the compounding staff and to protect the environment from the products produced.
Cleanroom design for USP 797 takes into consideration:
Rooms should be separated from surrounding unclassified spaces to reduce the risk of contaminants being blown, dragged or otherwise introduced into the HEPA filtered unidirectional air flow environment and this segregation should be continuously monitored.
Adequate HEPA filtered air flow is required to be supplied to the cleanroom and ante room to maintain cleanliness classification during operational activity through the number of air changes per hour. ISO Class 8 ante rooms must have a minimum of 15 air changes per hour of HEPA filtered air. ISO Class 7 spaces with PEC’s must have a minimum of 15 air changes per hour of HEPA filtered air and a minimum of 30 air changes per hour including the PEC’s. ISO Class 7 or lower spaces without PEC’s must have a minimum of 30 air changes per hour of HEPA filtered air. Ventilation efficiency includes HEPA filtered supply air introduced at the ceiling with low sidewall mounted return air, creating a general top down dilution of room air with HEPA filtered make-up air.
Hazardous drugs shall be stored separate from other inventory with a minimum of 12 air changes per hour maintaining a negative pressure relationship to adjoining spaces. Hazardous drugs shall be compounded in a physically separated area maintaining a minimum negative pressurization of 0.02 – 0.05 in. w.c. and have a minimum of 30 air changes per hour of HEPA filtered air. General construction of spaces must account for building tightness needed to maintain space pressure and cleanliness requirements. Surfaces must withstand continuous cleaning and disinfecting agents. No gaps or crevices for microorganisms to accumulate and grow.
Monitoring differential pressure between spaces is accomplished by permanently mounted room differential pressurization gauges. Pressure from ISO Class 7 to non classed area should be a minimum of 0.02 – 0.05 in. w.c. Measure pressure from cleanroom to gowning (ante room) and Gowning to prep area. Temperature conditions need to take occupant garbing into consideration as such the recommended range is 65 – 70 degrees F to maintain occupant comfort. Humidity considerations such as microbial growth, effects on products and processes, worker comfort and static electricity have established a recommended humidity of 30 – 60 % RH.
Primary Engineering Controls (PECs) are critical to the successful compliance with 797. Devices such as Laminar Flow Work Benches, Isolators and Biological Safety Cabinets should be placed within a buffer room in a manner to avoid conditions that could adversely affect its operation; doors opening and closing, personnel traffic, cross drafts from HVAC, and impact of other airflow devices. These devices for compounding shall be unidirectional laminar flow and because of the particle collection efficiency of the filter the first air at the face of the filter is for the purpose of aseptic compounding free from airborne particle contamination.