USP <797> categorizes contamination risk in the preparation of compounded sterile preparations (CSPs). A determination of the level of risk should be made for each facility where CSPs are compounded to assure that policies and practices established for the area respond to the risk level present. The three levels of risk are low, medium and high. All CSPs must be prepared in an ISO Class 5 environment, as is also required by the Joint Commission Medication Management requirement.

The primary area required to accommodate preparation of CSPs (in order from cleanest to dirtiest) are a Direct Compounding Area (DCA)/ Primary Engineering Control Area (PEC), a buffer area, and an ante room. These areas must be separated from the rest of the pharmacy.

Direct Compounding Area (DCA) and Primary Engineering Control) (ISO Class 5)

The primary engineering control (PEC) typically is a hooded area that is certified to ISO 5 environment. Equipment can be used to provide PEC includes laminar flow hoods, biosafety cabinets, compounding aseptic isolators, and compounding aseptic containment isolators.

Buffer Area (ISO Class 7)

The area around the PEC is called the buffer area, which is certified as an ISO Class 7 environment. Activities occurring in the buffer area typically include preparation and staging of components and supplies to be used in the compounding process.

Ante room (ISO class 8)

The ante room is the area immediately outside the buffer area, it should be certified as an ISO Class 8 environment. The Ante and Buffer areas require HEPA-Filtered air of not less than 30 ACH.

For more information see the ASHE Monograph by Chad Beebe at

USP 797

Pharmacy Physical Environmental areas as defined in USP <797>

ISO 14644 Standards

ISO 14644 Standards were first formed from the US Federal Standard 209E Airborne Particulate Cleanliness Classes in Cleanrooms and Clean Zones. ISO Classes refer to the particulate count in a room, with the lower classes being cleaner and higher classes having higher particulate count. An ISO Class 9 area is comparable to unfiltered urban air. Every lower class is a factor of 10 cleaner, or rather, 90% of the particles have been removed. So relative to ISO Class 9, an ISO Class 8 room has 90% of the particles removed, and an ISO Class 5 room has 99.99% of the particles removed.

IC Sentinel®

IC Sentinel® has a sophisticated 4 channel particle counter which is able to accurately count particles of different sizes as specified by ISO 14644. IC Sentinel® can be used in Pharmacy Anterooms, Buffer, and Primary Engineering Control (PEC) areas to continuously verify that ISO Class levels specified in USP <797> are satisfied. IC Sentinel® can also monitor other factors important in Pharmacy areas including differential pressure and humidity. IC Sentinel® can generate historical reports of air cleanliness, differential pressure, and humidity, and send alerts when thresholds are exceeded.