确定生产无菌药品的背景环境——B级区换气次数的方法

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

在乱流条件下实现5级洁净度并保证所需要的自净时间是生物医药行业及国内外空气洁净领域的一个新问题，对于所需送风量这一关键参数，目前尚无普适性的计算方法供设计人员参考，这对于新版GMP的实施造成了实质性的操作困难。采用不均匀分布计算理论和扩大主流区理论相结合的办法，提出了根据工程具体情况计算B级区换气次数的方法。对于文中所给出的范例，按该方法计算出的B级区换气次数下限为40h1左右，自净时间即可满足不超过GMP所要求的20min。若将自净时间限定为从7级自净到5级，则换气次数下限可低至30h叫以下。文中给出的换气次数比目前60~80h1的经验值小40％～60％，并为实测所验证，现行GMPB级区的净化空调设计可以用非常节能的办法实现。

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.