Method for determining air changes of GMP Grade B area—the background area for manufacturing sterile medicinal products

Using non-unidirection air flow to provide ISO 5 cleanliness is a new problem faced the air cleaning industry of China and the whole world. No well accepted calculation method of the required air supply is by far available for cleanroom designers, which leads to the difficulty for the execution of the new GMP regulation. Based on the uneven distribution theory and expanded mainstream theory, presents a method for determining air changes (ACH) of Grade B area according to specific applications. According to the discussed examples, the calculated lower limit of ACH needed for providing clean up period less than 20 minutes required by the GMP regulation is about 40 per hour. If the clean up period is defined as the time from operation status of ISO 7 to at rest status of ISO 5, the lower limit of ACH could be as low as 30 per hour or even lower. The calculation results could be 40 to 60 percent lower than the currently recommended 60 to 80 per hour. This conclusion is validated by field tests. In general, the clean HVAC system for Grade B area could be designed in a considerable energy saving way like this.