What is 'contact time' and why is it relevant for wipe sampling?

• A. The time between wiping and sample extraction in the lab.
• B. The speed at which the surface is wiped.
• C. The duration the wipe stays in contact with a surface during sampling, to recover dust; insufficient contact can affect results.
• D. The duration of the entire sampling session.

Answer: (C)

Contact time is the duration the wipe remains in contact with the surface while you’re collecting dust. This matters because how long the wipe is touching the surface under consistent pressure determines how much material can transfer from the surface to the wipe. If you lift or remove the wipe too quickly, dust particles may not detach and be captured, which can lead to underestimating contamination. This concept is about the actual pickup during sampling, not the time spent processing the sample in the lab, how fast you wipe, or the total length of the sampling session. In practice, protocols emphasize keeping a consistent, sufficient contact time to ensure the wipe collects an accurate portion of the surface dust for analysis.