This sections is from the AS-AP autosampler manual:
4.3 Condensation on Vial Tops and Well Plate Covers
Under certain operating conditions, condensation can form on the vial tops or
well plate covers. For example, this can occur if the tray temperature set point
is at 4 °C and the ambient temperature and relative humidity in the laboratory
are above 25 °C and 60% humidity. To prevent condensation from forming,
use one or more of the following methods:
• Ensure that the laboratory temperature remains below 25 °C and the
humidity below 60%.
• Increase the tray temperature set point (if the option is installed).
• Turn on the condensation fan. The fan blows air recycled from the
carousel area onto the top of the vials or well plates and prevents
condensation from forming.
To turn on the condensation fan, open the autosampler ePanel (in
Chromeleon 7) or Control panel (in Chromeleon 6.

and press F8. Under
Sampler, set the CondensationFan property to Normal or Max.
• On each injection, the carousel cover is opened to allow the needle to
access the vial. This introduces additional moist air from the lab
environment into the vial area. If the tray temperature control option is
installed and the condensation fan is set to Normal or Max, the carousel
automatically rotates after the injection operation is complete. This
distributes the moist air and prevents it from condensing on the vial caps
directly under the opening. The TrayRotationNumber property controls
the number of rotations (either 2 times, 1 time, or 0 times). The default is
2 rotations.
Thank you emeulman and Arne for your replies!!
We checked the fan and it is working. We even switched the fan to operate at "MAX", but we still have condensation.
For days we measure the humidity in the room and it is around 50-60%, the temperature around 20oC. We are located in Brazil, maybe the weather does not help…
My concern is if this could harm the samples somehow, eg. If there is water compensated on the top of vials, then when the needle reaches the sample, maybe this water could contaminate or dilute the sample… or is it just paranoia?!?!