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Physical Environment Provisions of USP <797> “Pharmaceutical Compounding—Sterile Preparations”

Originally Published:
Key Point Summary
Key Concepts/Context

USP <797> reports standards and policies for all physical environments in which compounded sterile preparations (CSPs) are prepared, packaged, and stored. The standards apply specifically to people who prepare CSPs and must take care to reduce the risk of contamination from their behaviors, hygiene, and clothing (i.e., garb). Clinical workers whose work lies within this realm must be individually trained and evaluated to maintain the standards and reduce microbial contamination that results from contact. The author explains the categorization of CSP contamination risk levels (low, medium, and high) and hones in on environmental quality and control measures in compounding areas to reduce airborne and surface contamination through measures such as hand-washing, cleaning surfaces, wearing appropriate materials/clothing, and proper ventilation.


The purpose of this monograph is to describe physical environment aspects of USP <797> and alert healthcare facility managers about the standards, policies, and practices that may help reduce the risk of CSP contamination during compounding and preparation of CSPs.


To reduce the risk of contamination during preparation, packaging, and storage of CSPs, the author recommends certain environmental/design considerations, starting with specific requirements for the layout of spaces for preparing sterile compounds and including the proper design of the ventilation system. These spaces exist in layers and include at the innermost and cleanest layer, the direct compounding area, which lies within the primary engineering control (PEC) area (which should be ISO Class 5). Surrounding those areas are the buffer area (ISO Class 7) and then the anteroom (ISO Class 7 or 8), which both require HEPA-filtered air of no less than 30 air changes per hour (ACH). The author encourages the use of a checklist during design and planning of these areas to ensure that regulations are being met, from the type of hood being used in the PEC, to proper air changes and use of impervious surfaces in the buffer area, to supply air being provided at the ceiling level and pressure differentials allowing for the separation of the anteroom to other areas, among other recommendations and requirements.

Design Category
Interior Material|Room configuration and layout|Ventilation and air-conditioning system
Outcome Category
HAI related outcomes
Environmental Condition Category
Environmental hygiene
Primary Author
Beebe, C.