Pharmaceutical water systems (PW and WFI) require a ventilating filter on the storage tank. It prevents dirty ambient air from being sucked into the system when water is withdrawn from the tank. This is often referred to as a sterile filter. However, there are numerous requirements for "real" sterile filtration according to the current EU GMP Annex 1. But is sterile filtration necessary at all for this application?
制药用水系统（PW 和 WFI）需要在储罐上安装呼吸过滤器。当水从水箱中抽出时，它可以防止肮脏的环境空气被吸入储罐中。这通常被称为无菌过滤器。但是，根据当前的欧盟GMP附录1，对“真正的”无菌过滤有许多要求。但是，对于这种应用，无菌过滤是必须的吗？
First of all, it is important to understand that pharmaceutical water systems, neither PW nor WFI systems, are or have to be sterile. The maximum permissible bacterial counts are specified in the pharmacopoeias (max. 100 cfu / ml for PW and max. 10 cfu /100 ml for WFI). PW and WFI bulk is therefore not "sterile" water. Therefore, no "sterile filter" is required as a vent filter. Even though tank vent filters are usually 0.2 µm filters, which are also used similarly for sterile filtration, they should not be called sterile filters for this application.
首先，有必要要了解制药用水系统，无论是纯化水系统还是注射用水系统，都不是无菌或不是必须无菌。药典中规定了最大允许细菌计数（PW最大100 cfu / ml，WFI最大10 cfu / 100 ml）。因此，PW和WFI不是“无菌”水。因此，不需要“无菌过滤器”作为呼吸过滤器。尽管储罐的呼吸过滤器通常是0.2μm过滤器，也类似地用于无菌过滤，但对于此应用，它们不应称为无菌过滤器。
However, testing of the integrity of the WFI tank filter is necessary - the current EU GMP Annex 1 requires it for WFI systems:
但是，有必要对WFI储罐的过滤器进行完整性测试 - 当前的欧盟GMP附录1要求：
6.11Where WFI storage tanks are equipped with hydrophobic bacteria retentive vent filters, the filters should not be a source of contamination and the integrity of the filter tested before installation and after use. Controls should be in place to prevent condensation formation on the filter (e.g. by heating).
6.11如果WFI储罐装有疏水性细菌滞留呼吸过滤器，则过滤器不应成为污染源，并应在安装前和使用后测试过滤器的完整性。应采取适当的控制措施，以防止过滤器上形成冷凝（例如通过加热）。
The requirement to test such WFI tank filters "in place" for integrity and to sterilise them has - after long discussion - been deliberately deleted from the now valid Annex 1. The majority of the authors could be convinced that such a strict requirement would have meant unnecessary additional costs and additional GMP risks for 99% of the WFI systems - and would thus ultimately harm rather than benefit the patient.
经过长时间的讨论，对这种WFI储罐过滤器进行“在线”完整性测试并对其进行消毒的要求已从现行版附录1中删除。大多数撰写人员相信，太过严格的要求将意味着99%的WFI系统将产生不必要的额外费用和额外的GMP风险 - 因此最终会损害而不是使患者受益。
