If visual examinationis used to supplement swab or rinse sampling, such determination of a visual detection limitmay be done but is not required. 

如果目检只是作为擦拭或冲洗取样的补充，则可以但不必要确定“目视检测限”。

A visual detection limit under specified viewing conditions can bedetermined by spiking coupons of the equipment surface materials with solutions of the residue atdifferent levels (in μg/cm2), and having a panel of trained observers determine the lowest level atwhich residues are clearly visible across the spiked surface. The significance of such a visual detectionlimit is that if equipment surfaces are determined to be visually clean under the same (or more stringent)viewing conditions in a cleaning validation protocolthe level of the residue is below the visualdetection limit. Appropriate viewing conditions include distance, lighting and angle. The visual limitdepends on the nature of the residue as well as the nature of the surface (e.g., stainless steel vs. PTFE)and the visual acuity of the inspector. Typical values reported in the literature for a visual detectionlimit are 1-4 μg/cm2 (23).For this determination, a percent recovery is not established;the purpose isto establish a value where residues are clearly visible so that any surface observed as visually clean isclearly below that value.

指定观察条件下的目视检测限可以通过在设备材质试样上涂布不同浓度（ μg/cm2） 的残留物来确定。 并需要一组训练有素的观察者来确定表面残留物明显可见时的最低残留水平。 目视检测限的意义在于， 如果在清洁验证方案中，在同样（或更严格）的观察条件下确定设备表面已目检洁净，则可认为实际残留水平低于目视检测限。适当的观察条件包括距离，光照以及观察角度。 目视检测限取决于残留物性质，表面性质（例如，不锈钢对PTFE）以及观察者的视力。文献报道的典型的目视检测限是1-4 μg/cm2。对于目视检测限，不需要确定百分回收率。该研究的目的是确定残留物明显可见时的一个残留物水平， 这样目视洁净的任何表面上残留水平都低于目视检测限。

关于如何确定可见残留限度的方法，请查看历史文章《如何确定清洁验证可见残留限度》。