Abstract
The risk for contamination in a pharmaceutical cleanroom was investigated through tracer gas measurements in 13 different scenarios, when the aerodynamic barrier between an airlock (AL) and a cleanroom (CR) was weakened by opening the door separating the rooms. Air velocities through the doorway, differential temperature between the airlock and the cleanroom, different door opening speeds and different walking paces of a mannequin entering the cleanroom were the four parameters in focus. The study was conducted in a full-scale cleanroom mock-up (4.7 x 3.5 x 2.5 m), where each scenario was repeated three times. The results of the investigation show that air velocity through the doorway is the most important design parameter to ensure the aerodynamic barrier, when an average air velocity between 0.14 m/s (resulted in 209 l of migrated air) and 0.33 m/s (resulted in 62 l of migrated air), which was achieved at isothermal conditions and with a door opening time of 10 seconds. Increasing the door opening time to 20 seconds diminishes the effect of a higher air velocity to neglectable levels. Last by not least, the differential temperature between airlock and cleanroom has an impact on the air migration, where a warm cleanroom (24 °C) and a cold airlock (20 °C) showed a low contamination risk with a door opening time of 10 seconds. A warm cleanroom (24 °C) and a cold airlock (20 °C) showed on the other hand a high level of air migration with almost 1.500 l of contaminated air entering the clean zone with a door opening of time 10 seconds.
Highlights
In the pharmaceutical production industry, controlled environments are used a mean to secure the medicine against contamination
The results of the investigation show that air velocity through the doorway is the most important design parameter to ensure the aerodynamic barrier, when an average air velocity between 0.14 m/s and 0.33 m/s, which was achieved at isothermal conditions and with a door opening time of 10 seconds
The differential temperature between airlock and cleanroom has an impact on the air migration, where a warm cleanroom (24 °C) and a cold airlock (20 °C) showed a low contamination risk with a door opening time of 10 seconds
Summary
In the pharmaceutical production industry, controlled environments are used a mean to secure the medicine against contamination. An aseptic controlled environment, where medicine production takes place, consists usually of a cleanroom with one or more adjacent airlocks. When the door between cleanroom and airlock is being opened, the overpressure ceases to exist, and the aerodynamic barrier is as a result weakened. To secure a cleanroom against contamination, the current guidelines from FDA and EU offer design criteria concerning the design of the facility such as differential overpressure between a cleanroom and an airlock and minimum air changes [2,3]. Research regarding the minimum required air velocity through the doorway for securing the barrier has been conducted intensively by Ljungqvist and Reinmuller and Whyte and Farquharson respectively
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