Potential for airborne contamination in turbulent- and unidirectional-airflow compounding aseptic isolators

Purpose. The ability of turbulent- and unidirectional-airflow compounding aseptic isolators (CAls) to control airborne contamination during aseptic compounding of compounded sterile preparations (CSPs) was studied. Methods. A three-phase challenge of the comparative airborne-contamination management capabilities of five CAls was conducted using augmented, industry-standard visual tracer and discrete particle counting methods. In phase 1, a visual smoke tracer was used to conduct a standardized, comparative challenge. In phase 2, CAI operational contamination-control capabilities were measured in accordance with the International Organization for Standardization (ISO) class 5 air cleanliness conditions using a standardized CSP process qualification procedure. Alcohol drying times were also compared. In phase 3, the gross contamination clearance interval required to achieve the ISO class 5 condition after a gross contamination event was measured for each CAI. Results. All four unidirectional-airflow CAls met ISO class 5 cleanliness requirements throughout all testing phases and areas of the work zone and demonstrated alcohol drying times of 16 seconds or less. The turbulent-airflow CAI tested failed to achieve the ISO class 5 operating condition at any time during the testing and required alcohol drying times of six minutes. The unidirectional-airflow CAls tested met the laminar-airflow workstation-equivalency requirements of chapter 797 of the United States Pharmacopeia, pharmaceutical aseptic processing standards, the industry-standard definition of a closed isolator, and the rigorous demands of pharmacy and nursing sterile compounding. Conclusion. The performance of four unidirectional-flow CAls supports their use in pharmacy and nursing CSP operations, whereas the performance of one turbulent-flow CAI does not.