Which of the following is a method used for contamination analysis?

The patch test is a relevant method used for contamination analysis as it involves applying a small area of a substance to a specific location to observe any reactions or effects that may indicate contamination. This technique is particularly useful when assessing whether a particular material is safe for use or if it has been compromised in some way.

In the context of contamination analysis, the patch test allows for targeted examination of materials and surfaces, providing insights based on the reactions observed. It helps identify not only the presence of contaminants but also potential reactions to them, which can inform safety and procedural measures.

Other methods listed, such as fluid replacement and visual inspection, serve different purposes in maintenance and troubleshooting contexts. Fluid replacement typically involves substituting contaminated fluids with clean ones but does not analyze the contaminants themselves systematically. Visual inspection is essential for identifying general maintenance issues but may not provide sufficient detail regarding the nature or extent of contamination. Chemical analysis, although highly definitive for identifying contaminants, often requires sophisticated equipment and more extensive procedures, rather than the more straightforward approach offered by the patch test.